Having received the Augustus Caesar award at the Monarch level, I feel able to give some advice to beginners. Much of this is distilled from other sources, and it may not all work for you, but these concepts have helped me move up and may help you. I will welcome comments that may sharpen my understanding of the issues that arise in the early game.
Recommended Settings:
Continents
Temperate - Medium - Standard
English - Elizabeth (I like her combination of traits, her special unit, and her special building)
Difficulty: Start at Settler and move up every time you win one. After you lose one, win at least two before moving up.
Normal speed
After the Dawn of Man message, press Esc and Options; make sure "Automated Workers Leave Old Improvements" is checked. Then click Exit.
Move One:
Use your warrior to explore the area around your city. Priority squares are Tribal Villages, hills, and forests.
Build your first city where your settler is standing. As your experience progresses, you will learn when and where to move a settler, but you don't want to waste much time getting that first city under way.
Start building a worker.
Immediately start to research something relevant to the squares now painted white.
You're done!
More Early Moves:
Build the best military you can and use them to explore your surroundings.
At size 3, build another worker.
At size 5, build your first settler. Continue to build worker-settler-worker-settler until you run out of room to expand or your economy bogs down.
Use workers to improve food resources first, then start chopping to accelerate your production. Every time your worker finishes an improvement, check to see if the square says "Requires Route". If it does, and you need the additional benefits listed in the tool tip, make sure the improvement you just completed gets connected to your transportation network (this can be by road or by water). As long as there's enough food (notice the color of the city population indicator), I like to build cottages especially on the squares that have one gold already (there's a button that shows what each square produces that you'll want to turn on if it's not on already). Cottages eventually turn into towns, which help your economy a lot. In the case of Elizabeth, a cottage on a square with one commerce already will give you three commerce right away, one reason I like Liz! Farms are good on tiles that already have two or three bread. Tiles with just a hammer and a bread I often save for workshops.
Early Research priorities: Agriculture, Bronze Working if you have trees to chop, Animal Husbandry if you have a meat resource, Wheel, Pottery, Mysticism. Hunting if you have resources that need that tech. Archery if you don't have copper or horses.
Station some of your warriors near the best city locations you have found, and bring the rest closer to your city for escort duty. If you have horses, some chariots can be very helpful but keep your eye on the main thing, which is to grab as much land and resources as you can.
Good city locations will be near fresh water with some forests and hills, one or two food resources, close to other civs, and in a position to control important strategic resources: especially horses, copper and iron, elephants if you can't get horses, and commercial resources such as gems, precious metals, vineyards, and anything that requires "Calendar" to develop. Jungle squares are generally less productive and should be avoided until the better locations are gone. Land squares are generally more productive than water, but it's worth going after fish and other aquatic food resources, and it's nice to have harbors. Your second city should be up by 2000 BC and by 1000 BC you should have four healthy cities running. Aim for six by turn 100 if you can get there without slowing down research very much. If necessary, you can set some of your older cities to produce gold.
The Specialist Economy: better players swear by it! A typical array would be six cities:
One city with lots of food and some hills to build great people - a Library would be a typical early build here, and later the National Epic
Two cities with lots of hills and some farms where you can build military units - here you want your barracks, forges, factories, and Heroic Epic
Three cities with some farms and room for lots of cottages - here you build banks, Wall Street, etc.
Workers should precede Settlers to the new cities when possible. They can build roads and "pre-chop" forests while waiting (that means stop chopping when one turn of chopping remains). They often need military escort.
Always escort settlers and plant a defender in each new city.
About 1.5 workers per city is a reasonable ratio. Use one near each city and set the rest to "Build Trade Network".
Pay attention to the "Big Fat Cross" consisting of 20 squares surrounding each city. These are the squares your cities can "work" to get the most benefit from resources (but only after the city's cultural border expands to fill that area). If you get the BUG MOD (highly recommended) you can push Alt-X to paint the BFC around each city. I think that helps a lot! Resources outside the BFC can be developed after your cultural borders envelop them, but you get much less benefit. The same applies to chopping forests. If you double click on a city, you can see which tiles are currently being worked. At times you will need to override your "city manager" to get more production or food or commerce for a special need, so it's well to keep track of what each city is doing.
Your new cities should usually start with a monument and granary. Stonehenge is a useful wonder because it will give you a free monument in each city, greatly helping your early cultural spread. Every city will need a couple of defenders by the time barbarian warriors start popping up. Also consider guarding key resources such as a horse pasture or iron mine, especially if you have only one and most especially if that one is near your border.
If you are getting raided by barbarians, build axemen if you can, otherwise chariots. Station them to intercept barbarians and to prevent the Barbs from spawning near your borders. You can also use chariots to explore dark areas and other civs who will agree to Open Borders.
Managing Early Development:
Libraries should be an early priority. They boost research and allow you to run scientist specialists in cities that have extra food. You will soon start to hatch "Great" scientists who can then build Academies in your cities that already have strong research programs (look on the Cities screen for the beaker count). One of the easiest routes to victory is to get way ahead of your competition technologically. Then you can send your much-stronger military to take over rival cities with minimal loss of your units. Some of the obvious benefits of expanding through conquest are stronger economy, appropriating wonders you didn't have to build, and acquiring vassals who will provide you with free resources, buffer your core cities against aggressive rivals, and vote for you in diplomatic elections. You get half of your vassals' land and population points towards a domination victory, and they can't attack you while your back is turned. If you stay strong, a vassal will rarely leave you.
You will probably not be able to keep your research slider at 100% when you have five cities going. It's wise to leave about one gold in your treasury for each turn elapsed: 50 gold at turn 50 for example. The ability to immediately upgrade units can save your city during a surprise attack, and you can trade technologies more easily if you have some gold to offer.
Hereditary Rule is especially helpful when you have unhappy citizens slowing a city's progress. Additional military units are a cheap way to manage this problem.
Libraries, Monasteries, and other "culture" buildings are helpful if a rival civilization is taking squares away from your cities.
If you have horses or elephants, research Horseback Riding. Horse Archers can give you a tremendous edge because they can get to the scene of the action much faster than infantry. Later you can upgrade them to Knights, Cuirassiers, Cavalry, and Helicopter Gunships. These are all excellent things to have!
Elephants are slow but will devastate mounted enemies. The same is true for Spearmen, so keep an eye on what your rivals are building. Axemen are good defenders of cities and resources who can sortie as needed to deal with raiding parties. Archers are particularly good city defenders and can eventually be upgraded to Longbows, which are about as strong as muskets at defense.
Iron Working is vital if you don't have copper, and good even if you do; jungle squares can't be cleared without Iron Working.
Barbarian civilizations are a nuisance because they live by raiding their neighbors. Your mounted units can take them over at your convenience. In general, expect barbarian incursions and use them to give your units experience points. The exception is if there's a "Massive Barbarian Uprising" on your borders, in which case you need to drop everything and scramble to wipe them out.
Bureaucracy and Free Market are good civics as you approach the Middle Ages. As your empire expands, State Property can save you a bunch of gold.
I like to save my game every twenty moves in the first hundred and every ten moves thereafter. You can also set your game to auto-save every move, which allows you to correct those stupid interface blunders that send your units to the wrong square. This also facilitates trying different tactics so the price of failure isn't so high that you're afraid to try something. Don't be afraid of making mistakes; just be sure to learn from them so you can make NEW mistakes next time!
Tech development is a matter of judgment and experience. You may wish to grab the Oracle for the free technology it gives you. One productive strategy is to "bee-line" through Writing up to Liberalism, which gives you a free tech and up to two religions. You can choose Nationalism as your freebie and then start the Taj Mahal, which gives you a Golden Age. If you have a good trading partner, you can probably trade your higher techs for the lesser ones you missed along the road. The challenge here is to judge how much you can afford to be behind in the arms race, given the disposition of your neighbors. Watch out especially for Montezuma, who will attack you just for sport!
SLAVERY is as important as it is distasteful. Realistically, this is how most civilizations operated until the late Twentieth Century, and many still do. I found it impossible to do well on Monarch without using Slavery. You'll need this about the time your capitol gets to size 5. Look on the details screen for each city to see if it makes sense to "whip" your current production. Don't whip fewer than two citizens at a time. Do whip when you have unhappy citizens (they eat but don't produce, so you can turn them into production with minimal regret). Some combination of chopping and whipping can help you complete a World Wonder ahead of the competition. It's also useful when you need a military unit yesterday (it won't be there until tomorrow but that's sometimes much better than waiting five turns). Another good time for whipping is during a war when unhappiness rises and production consequently drops. Your cities may even begin to starve, so you might as well get some use from the "surplus population." A newly-captured city also provides good whipping opportunities if it's size 5 or greater. As soon as the city is pacified, it may start to starve because it doesn't have access to nearby food resources that it previously relied on. The first thing you want to build will be something to add to your new city's culture output, but it may take a long time with limited access to industrial resources and a lot of starving, unhappy citizens. Whip that first building for two or more citizens and see your troubles go away fast!
After Move 100:
Get into the habit of checking all the info buttons on the upper right of your screen every ten moves, so you understand in some depth how your development compares with your rivals. If your neighbor shows a dramatic increase in power, consider that one of your cities may be his intended target. You'll also see who is going for a culture victory, and later for the space race.
A typical strategy involves taking over your neighbor during the second hundred moves. Your invasion should include at least a couple of dozen units so you can capture and garrison at least four cities before your victim can get organized. Overwhelming numbers of mounted units work better for me than siege engines, which really slow things down. If you have enough espionage points, you can flip an enemy city into revolt for one turn. This is worth doing if the enemy city has a high defense rating and lots of strong units inside.
Eliminate your enemy's strategic metals, horse pastures and elephant camps early if you can. Multiple attack points will disorganize his defense. Here's where mounted units can give you a huge advantage: you can post them between or among enemy cities so the poor guy doesn't know which city you're about to attack. He has to spread his defense out to cover all your possible attack points. Use of siege engines gives your enemy time to reinforce and fortify.
When you start to bog down, see what he'll give you for a peace treaty. Use the ten turns to build up your forces and then hit him again. If he goes vassal to a stronger neighbor, grab what you quickly can and then wait for a peace opening.
If your neighbor offers to be your vassal, take it. You can grab all his resources. If you pass up the chance, he'll be somebody else's vassal pretty soon. The exception is if he's being invaded by people that you don't want to be at war with.
One way to manage an enemy who is close to you in strength is to invade one of his large cities that's close enough to your border that you can reach it in one or two turns after declaring war. Then dig in and wait for the inevitable counterattack. If you brought enough units, there's a good chance you'll be able to wipe out a large share of his military when he counterattacks, leaving only token resistance as you expand your attack to the cities nearby. Any time you can catch enemy forces in the open, that's better than trying to dig them out of an enemy city. There's a "No Unit Cycling" option you can select when you have a lot of units in action so the program will quit dragging your attention away from the area you are trying to focus on. Don't forget to turn this back off before you end your move so you see the units that haven't moved yet. It's also helpful to select the option that shows all enemy units, not just the ones in your territory... you have to pull your camera back to see that option.
Pillage is, you should pardon the expression, a double-edged sword. You pick up some gold, but if you plan to hold the territory you might rather have it unpillaged.
Don't be afraid to bypass smaller enemy cities to get at his strongholds; you can mop up the trash at your leisure. It's preferable to eradicate an enemy when you can, so his few remaining outposts don't encourage rebellion in the cities you have already taken. Really crummy cities you might rather raze than keep, but be prepared for spawning partisans and making your enemy really mad at you.
Attack cities near your border so your culture will spread into the new territory. Shave your enemy, consolidate, and then shave him again. A city that's too close to another civilization may soon flip away from you, so you may do better to gift it and get the relations boost, especially if you are "liberating" it back to its original owner.
By this time you should be checking frequently for trade opportunities. You will easily add 20 gold per turn that way. Also, you can trade some of your techs for others, hastening your overall development. Just be careful about trading the latest military technology to somebody you may end up at war with in the next few centuries. Trade agreements should be renegotiated every ten turns if the other party has at least two more gold to trade. You can wind up getting 20 gold at turn 400 for something that went for 2 gold in turn 200.
Longbows are your best city defenders in the medieval period. Spies may be needed to discourage enemies from sabotaging your cities, and they can also sortie to enemy cities as scouts, as saboteurs, and to raise the cost to your enemy of sabotage missions through counterespionage.
You may need a few more settlers to fill in nearby vacant spots, but only if you can keep your research slider above 50%. Don't worry if a rival plants a city in the middle of your doughnut: if you build culture in surrounding cities, you will likely cause his city to flip to your civilization. By that time, you may not really want it, but you can pick up all his improvements for free when you raze his pathetic city remnant.
One way to lose in the middle game is if a rival builds the Apostolic Palace and spreads his religion widely. Your options are: (1) quickly spread the AP religion to all your cities so you can grab the leadership and block hostile votes; (2) capture the city that has the AP; (3) if the AP religion is in none of your cities, Theocracy will immunize you against infection (and, if you have a state religion, give your new units experience points, which can make them play much stronger than their base rating).
If time allows, it's helpful to build a couple of caravels and a couple of explorers. Send them in opposite directions in an attempt to be the first to circumnavigate the globe, make contact with other civilizations, and explore the other continent. Being the first to circumnavigate the globe gives your navy a movement bonus, a big plus in subsequent naval actions. Your explorers may be able to meet in the middle of the other continent, which is often the fastest way to the circumnavigation award.
Once you get a dozen or more cities, your research and production capabilities should give you enough edge to pursue whatever style of victory appeals to you.
If you have nine cities, you have a platform for a culture win. You want three religions in each city with three temples in each city, eventually allowing you to build the culture-multiplier holy building for each religion in each of your three main culture cities, along with all the Great Artists and cultural wonders you can get. Of course you'll want to guard your borders but you don't have to go beyond rifling for that (the Redcoat is a terrific asset).
In any case, if you found a religion you want to build that religion's holy shrine as soon as you can and spread your religion widely by building missionaries. Each city with your religion will pay you one gold per turn. That can really add up over the course of a few hundred moves!
Recommended Settings:
Continents
Temperate - Medium - Standard
English - Elizabeth (I like her combination of traits, her special unit, and her special building)
Difficulty: Start at Settler and move up every time you win one. After you lose one, win at least two before moving up.
Normal speed
After the Dawn of Man message, press Esc and Options; make sure "Automated Workers Leave Old Improvements" is checked. Then click Exit.
Move One:
Use your warrior to explore the area around your city. Priority squares are Tribal Villages, hills, and forests.
Build your first city where your settler is standing. As your experience progresses, you will learn when and where to move a settler, but you don't want to waste much time getting that first city under way.
Start building a worker.
Immediately start to research something relevant to the squares now painted white.
You're done!
More Early Moves:
Build the best military you can and use them to explore your surroundings.
At size 3, build another worker.
At size 5, build your first settler. Continue to build worker-settler-worker-settler until you run out of room to expand or your economy bogs down.
Use workers to improve food resources first, then start chopping to accelerate your production. Every time your worker finishes an improvement, check to see if the square says "Requires Route". If it does, and you need the additional benefits listed in the tool tip, make sure the improvement you just completed gets connected to your transportation network (this can be by road or by water). As long as there's enough food (notice the color of the city population indicator), I like to build cottages especially on the squares that have one gold already (there's a button that shows what each square produces that you'll want to turn on if it's not on already). Cottages eventually turn into towns, which help your economy a lot. In the case of Elizabeth, a cottage on a square with one commerce already will give you three commerce right away, one reason I like Liz! Farms are good on tiles that already have two or three bread. Tiles with just a hammer and a bread I often save for workshops.
Early Research priorities: Agriculture, Bronze Working if you have trees to chop, Animal Husbandry if you have a meat resource, Wheel, Pottery, Mysticism. Hunting if you have resources that need that tech. Archery if you don't have copper or horses.
Station some of your warriors near the best city locations you have found, and bring the rest closer to your city for escort duty. If you have horses, some chariots can be very helpful but keep your eye on the main thing, which is to grab as much land and resources as you can.
Good city locations will be near fresh water with some forests and hills, one or two food resources, close to other civs, and in a position to control important strategic resources: especially horses, copper and iron, elephants if you can't get horses, and commercial resources such as gems, precious metals, vineyards, and anything that requires "Calendar" to develop. Jungle squares are generally less productive and should be avoided until the better locations are gone. Land squares are generally more productive than water, but it's worth going after fish and other aquatic food resources, and it's nice to have harbors. Your second city should be up by 2000 BC and by 1000 BC you should have four healthy cities running. Aim for six by turn 100 if you can get there without slowing down research very much. If necessary, you can set some of your older cities to produce gold.
The Specialist Economy: better players swear by it! A typical array would be six cities:
One city with lots of food and some hills to build great people - a Library would be a typical early build here, and later the National Epic
Two cities with lots of hills and some farms where you can build military units - here you want your barracks, forges, factories, and Heroic Epic
Three cities with some farms and room for lots of cottages - here you build banks, Wall Street, etc.
Workers should precede Settlers to the new cities when possible. They can build roads and "pre-chop" forests while waiting (that means stop chopping when one turn of chopping remains). They often need military escort.
Always escort settlers and plant a defender in each new city.
About 1.5 workers per city is a reasonable ratio. Use one near each city and set the rest to "Build Trade Network".
Pay attention to the "Big Fat Cross" consisting of 20 squares surrounding each city. These are the squares your cities can "work" to get the most benefit from resources (but only after the city's cultural border expands to fill that area). If you get the BUG MOD (highly recommended) you can push Alt-X to paint the BFC around each city. I think that helps a lot! Resources outside the BFC can be developed after your cultural borders envelop them, but you get much less benefit. The same applies to chopping forests. If you double click on a city, you can see which tiles are currently being worked. At times you will need to override your "city manager" to get more production or food or commerce for a special need, so it's well to keep track of what each city is doing.
Your new cities should usually start with a monument and granary. Stonehenge is a useful wonder because it will give you a free monument in each city, greatly helping your early cultural spread. Every city will need a couple of defenders by the time barbarian warriors start popping up. Also consider guarding key resources such as a horse pasture or iron mine, especially if you have only one and most especially if that one is near your border.
If you are getting raided by barbarians, build axemen if you can, otherwise chariots. Station them to intercept barbarians and to prevent the Barbs from spawning near your borders. You can also use chariots to explore dark areas and other civs who will agree to Open Borders.
Managing Early Development:
Libraries should be an early priority. They boost research and allow you to run scientist specialists in cities that have extra food. You will soon start to hatch "Great" scientists who can then build Academies in your cities that already have strong research programs (look on the Cities screen for the beaker count). One of the easiest routes to victory is to get way ahead of your competition technologically. Then you can send your much-stronger military to take over rival cities with minimal loss of your units. Some of the obvious benefits of expanding through conquest are stronger economy, appropriating wonders you didn't have to build, and acquiring vassals who will provide you with free resources, buffer your core cities against aggressive rivals, and vote for you in diplomatic elections. You get half of your vassals' land and population points towards a domination victory, and they can't attack you while your back is turned. If you stay strong, a vassal will rarely leave you.
You will probably not be able to keep your research slider at 100% when you have five cities going. It's wise to leave about one gold in your treasury for each turn elapsed: 50 gold at turn 50 for example. The ability to immediately upgrade units can save your city during a surprise attack, and you can trade technologies more easily if you have some gold to offer.
Hereditary Rule is especially helpful when you have unhappy citizens slowing a city's progress. Additional military units are a cheap way to manage this problem.
Libraries, Monasteries, and other "culture" buildings are helpful if a rival civilization is taking squares away from your cities.
If you have horses or elephants, research Horseback Riding. Horse Archers can give you a tremendous edge because they can get to the scene of the action much faster than infantry. Later you can upgrade them to Knights, Cuirassiers, Cavalry, and Helicopter Gunships. These are all excellent things to have!
Elephants are slow but will devastate mounted enemies. The same is true for Spearmen, so keep an eye on what your rivals are building. Axemen are good defenders of cities and resources who can sortie as needed to deal with raiding parties. Archers are particularly good city defenders and can eventually be upgraded to Longbows, which are about as strong as muskets at defense.
Iron Working is vital if you don't have copper, and good even if you do; jungle squares can't be cleared without Iron Working.
Barbarian civilizations are a nuisance because they live by raiding their neighbors. Your mounted units can take them over at your convenience. In general, expect barbarian incursions and use them to give your units experience points. The exception is if there's a "Massive Barbarian Uprising" on your borders, in which case you need to drop everything and scramble to wipe them out.
Bureaucracy and Free Market are good civics as you approach the Middle Ages. As your empire expands, State Property can save you a bunch of gold.
I like to save my game every twenty moves in the first hundred and every ten moves thereafter. You can also set your game to auto-save every move, which allows you to correct those stupid interface blunders that send your units to the wrong square. This also facilitates trying different tactics so the price of failure isn't so high that you're afraid to try something. Don't be afraid of making mistakes; just be sure to learn from them so you can make NEW mistakes next time!
Tech development is a matter of judgment and experience. You may wish to grab the Oracle for the free technology it gives you. One productive strategy is to "bee-line" through Writing up to Liberalism, which gives you a free tech and up to two religions. You can choose Nationalism as your freebie and then start the Taj Mahal, which gives you a Golden Age. If you have a good trading partner, you can probably trade your higher techs for the lesser ones you missed along the road. The challenge here is to judge how much you can afford to be behind in the arms race, given the disposition of your neighbors. Watch out especially for Montezuma, who will attack you just for sport!
SLAVERY is as important as it is distasteful. Realistically, this is how most civilizations operated until the late Twentieth Century, and many still do. I found it impossible to do well on Monarch without using Slavery. You'll need this about the time your capitol gets to size 5. Look on the details screen for each city to see if it makes sense to "whip" your current production. Don't whip fewer than two citizens at a time. Do whip when you have unhappy citizens (they eat but don't produce, so you can turn them into production with minimal regret). Some combination of chopping and whipping can help you complete a World Wonder ahead of the competition. It's also useful when you need a military unit yesterday (it won't be there until tomorrow but that's sometimes much better than waiting five turns). Another good time for whipping is during a war when unhappiness rises and production consequently drops. Your cities may even begin to starve, so you might as well get some use from the "surplus population." A newly-captured city also provides good whipping opportunities if it's size 5 or greater. As soon as the city is pacified, it may start to starve because it doesn't have access to nearby food resources that it previously relied on. The first thing you want to build will be something to add to your new city's culture output, but it may take a long time with limited access to industrial resources and a lot of starving, unhappy citizens. Whip that first building for two or more citizens and see your troubles go away fast!
After Move 100:
Get into the habit of checking all the info buttons on the upper right of your screen every ten moves, so you understand in some depth how your development compares with your rivals. If your neighbor shows a dramatic increase in power, consider that one of your cities may be his intended target. You'll also see who is going for a culture victory, and later for the space race.
A typical strategy involves taking over your neighbor during the second hundred moves. Your invasion should include at least a couple of dozen units so you can capture and garrison at least four cities before your victim can get organized. Overwhelming numbers of mounted units work better for me than siege engines, which really slow things down. If you have enough espionage points, you can flip an enemy city into revolt for one turn. This is worth doing if the enemy city has a high defense rating and lots of strong units inside.
Eliminate your enemy's strategic metals, horse pastures and elephant camps early if you can. Multiple attack points will disorganize his defense. Here's where mounted units can give you a huge advantage: you can post them between or among enemy cities so the poor guy doesn't know which city you're about to attack. He has to spread his defense out to cover all your possible attack points. Use of siege engines gives your enemy time to reinforce and fortify.
When you start to bog down, see what he'll give you for a peace treaty. Use the ten turns to build up your forces and then hit him again. If he goes vassal to a stronger neighbor, grab what you quickly can and then wait for a peace opening.
If your neighbor offers to be your vassal, take it. You can grab all his resources. If you pass up the chance, he'll be somebody else's vassal pretty soon. The exception is if he's being invaded by people that you don't want to be at war with.
One way to manage an enemy who is close to you in strength is to invade one of his large cities that's close enough to your border that you can reach it in one or two turns after declaring war. Then dig in and wait for the inevitable counterattack. If you brought enough units, there's a good chance you'll be able to wipe out a large share of his military when he counterattacks, leaving only token resistance as you expand your attack to the cities nearby. Any time you can catch enemy forces in the open, that's better than trying to dig them out of an enemy city. There's a "No Unit Cycling" option you can select when you have a lot of units in action so the program will quit dragging your attention away from the area you are trying to focus on. Don't forget to turn this back off before you end your move so you see the units that haven't moved yet. It's also helpful to select the option that shows all enemy units, not just the ones in your territory... you have to pull your camera back to see that option.
Pillage is, you should pardon the expression, a double-edged sword. You pick up some gold, but if you plan to hold the territory you might rather have it unpillaged.
Don't be afraid to bypass smaller enemy cities to get at his strongholds; you can mop up the trash at your leisure. It's preferable to eradicate an enemy when you can, so his few remaining outposts don't encourage rebellion in the cities you have already taken. Really crummy cities you might rather raze than keep, but be prepared for spawning partisans and making your enemy really mad at you.
Attack cities near your border so your culture will spread into the new territory. Shave your enemy, consolidate, and then shave him again. A city that's too close to another civilization may soon flip away from you, so you may do better to gift it and get the relations boost, especially if you are "liberating" it back to its original owner.
By this time you should be checking frequently for trade opportunities. You will easily add 20 gold per turn that way. Also, you can trade some of your techs for others, hastening your overall development. Just be careful about trading the latest military technology to somebody you may end up at war with in the next few centuries. Trade agreements should be renegotiated every ten turns if the other party has at least two more gold to trade. You can wind up getting 20 gold at turn 400 for something that went for 2 gold in turn 200.
Longbows are your best city defenders in the medieval period. Spies may be needed to discourage enemies from sabotaging your cities, and they can also sortie to enemy cities as scouts, as saboteurs, and to raise the cost to your enemy of sabotage missions through counterespionage.
You may need a few more settlers to fill in nearby vacant spots, but only if you can keep your research slider above 50%. Don't worry if a rival plants a city in the middle of your doughnut: if you build culture in surrounding cities, you will likely cause his city to flip to your civilization. By that time, you may not really want it, but you can pick up all his improvements for free when you raze his pathetic city remnant.
One way to lose in the middle game is if a rival builds the Apostolic Palace and spreads his religion widely. Your options are: (1) quickly spread the AP religion to all your cities so you can grab the leadership and block hostile votes; (2) capture the city that has the AP; (3) if the AP religion is in none of your cities, Theocracy will immunize you against infection (and, if you have a state religion, give your new units experience points, which can make them play much stronger than their base rating).
If time allows, it's helpful to build a couple of caravels and a couple of explorers. Send them in opposite directions in an attempt to be the first to circumnavigate the globe, make contact with other civilizations, and explore the other continent. Being the first to circumnavigate the globe gives your navy a movement bonus, a big plus in subsequent naval actions. Your explorers may be able to meet in the middle of the other continent, which is often the fastest way to the circumnavigation award.
Once you get a dozen or more cities, your research and production capabilities should give you enough edge to pursue whatever style of victory appeals to you.
If you have nine cities, you have a platform for a culture win. You want three religions in each city with three temples in each city, eventually allowing you to build the culture-multiplier holy building for each religion in each of your three main culture cities, along with all the Great Artists and cultural wonders you can get. Of course you'll want to guard your borders but you don't have to go beyond rifling for that (the Redcoat is a terrific asset).
In any case, if you found a religion you want to build that religion's holy shrine as soon as you can and spread your religion widely by building missionaries. Each city with your religion will pay you one gold per turn. That can really add up over the course of a few hundred moves!
