Thank you for the suggestions.
Going Culture/Faith with an eye to doing CS quests seems a good starting plan for a Diplomatic Victory. Aiming for a Scientific Victory while terrorising my neighbours sounds like a good plan on improving my familiarity with combat without jumping right into the deep end. Perhaps use a military civ like Germany or Japan for the latter? With either, would I be better advised starting on smaller maps?
Smaller maps are generally easier for most victory conditions - if you're comfortable with large maps on Warlord, you may want to try a size or two smaller on Prince.
I pretty well always play Standard size, Standard time, standard rules (eg Barbarians, etc), start from year dot, pick a civ I have not won with before, and random opponents. I usually swing between Pangea and Continents, though I have thrown in Islands when playing a naval civ (eg England). Hey, I am not above playing to my advantages
I have played smaller and larger maps before, but Standard does feel a good size.
Japan is an odd one. As revised in the recent patch, it's instinctive to suggest it's best on archipelago maps, since it gets bonuses from atolls and fishing boats. However, it is still a warmonger civ and with a medieval land unit as a UU. This gives it a playstyle much better-suited to maps where you have rivals that are accessible by land, since by the time you hit Astronomy to allow quick passage across oceans for your invasion force, your military heyday has passed. Continents with a good amount of coast seem likely to be best for Japan.
I start my tech priorities by looking at what my starting luxuries are. If both use the same improvement (eg Plantation) I put that as my #1 priority. If they are split, I prioritise Plantations > Quarries > Camps and pick up ONE of them first and save the other until a little later.
That's generally a sound plan, but it's good to consider what the 'luxury tech' leads to (for example, if you have silver and gems, bear in mind not just whether you want Mining immediately, but also whether you want to rush the Bronze Working tech path). Unless you build workers immediately (and probably even if you do), a good general plan is to take Pottery first regardless of your starting situation, because it gives you access to granaries and shrines (valuable if you want early religion and aren't needing to go for Calendar immediately), and it leads directly to Writing.
In my own games, whether or not I tech to Writing immediately tends to depend a lot on my start. Unless I have a good food start, it is usually not worth it if there are better alternatives since a library is only valuable when you have a decent population size.
Policies, I tend to swing between Tradition and Liberty for my opening. I have never finished an Honour game to recollection and not yet opened with Piety (though intend to soon). My decision there usually comes down to what Civ I am playing (eg Tradition for Rome, Liberty for China). Since I usually ignore City States, I ignore Patronage. I use Aesthetics for Cultural and Rationalism for Science. I pretty well always pick up Commerce in BNW and end up swimming in money. I rarely play maritime-heavy, so Exploration is rarely useful to me. I cannot recall ever using Order or Autocracy in any version of the game, always running Freedom. I always fill whatever Social Policy I start and try to time my individual policies to what I need (eg pick up Collective Rule after The Wheel, then Meritocracy after Roads are completed). In BNW, I have been prioritising Freedom after unlocking it.
These all sound like sound general decisions that should serve you well above Warlord. It's usually a good idea to choose between Liberty and Tradition, for instance, based more on map context than civ selection (unless you specifically have a civ that benefits from playing either tall or wide) - if you don't have many good city spots in the landscape and good food and/or production to quickly train settlers, Liberty will generally not help a great deal.
Honor has its uses, contrary to its many critics here, but it is very specifically tailored to warmongering civs, and certain civs will get more out of it than others. It might be one to try with Japan, as Bushido will help in taking out barbarians quickly and you could get a very early head start culturally (although the Aztecs are better still in this regard).
Usually, if taking Piety you don't want to take, e.g. "full Liberty then full Piety" - you also don't want Piety as your first policy because it's the only starting tree whose opener doesn't give you a culture boost of some kind. So you will usually find yourself completing two trees in parallel; some Piety policies you want very early to maximise the effect (mainly, the opener and Organized Religion); you can usually then finish Liberty (or whatever - it could be Tradition, but religion is one area where wide empires are better than tall ones as a general rule) and return to Piety in time to get the first (or one of the first) Reformation beliefs.
For cities, I start by picking up
buildings, followed by
, then
. After that, I prioritise
or
, picking up lower-tier versions of the opposite when I have room. If I have no important buildings that take priority, I often build Wonders. I only build Wonders that provide notable benefits to my game (eg The Great Library, but not The Temple of Artemis).
As you improve your play, you'll find that in this specific case Artemis is usually a better investment than Great Library - a 10% growth bonus is significant.
Luxury resource = Plantation/Quarry/etc
* Special resource = Farm/Pasture/etc
* Riverside = Farm
* Hill = Mine
* Plain = Trading Post
* Grassland = Specialist improvement (eg Science Academy)
It's a good rule of thumb that, where possible, a tile should pay for the citizen working it - so a plain with 2 food, 1 production is better than one with 1 food, 1 production and 1 gold, for instance, since the citizen is costing you 2 food. At the same time you will need excess food in order to maximise growth, maintain specialists, and allow you to work mines, so don't neglect grassland farms (3 food) - grassland and rivers are however good places to site GP improvements (again, because they allow you to pay the food cost for the citizen working it).
I always found cities near Luxuries; ones I do not already have, if at all possible. I usually found them on river-sides, but will break from that if there are luxuries away from the rivers.
At the moment, rivers are mainly useful for trade cities, so only prioritise them if you have a diversity of resources in the area and potential trading partners. Usually river sites will be good general sites for settling cities, and the defensive bonus can be helpful, but you should probably be thinking "resources and hills first, rivers if associated with them" rather than "rivers first, luxuries if associated with them". Deserts are an obvious exception because of flood plains - it's very rare to find a useful desert city site that isn't associated with a river.
I also keep an eye open for a good mix of food and production, generally shying away from Deserts
A good tip is to specialise - you will want your production cities to have some food (and indeed your food cities to have some production), but an even mix is generally not as desirable as a hill city with a couple of wheat tiles, or a mostly grassland city with iron and a a couple of hills. The former can build units very quickly as needed and so act as your military city, and can also be a Wonder factory; the latter has enough production to build, e.g. universities, and enough food to place citizens in them as specialists.
Honestly, whether or not the city is on a Hill never comes into consideration. I usually cut down all the forests very early on to boost production, then build the appropriate improvement after each section is removed.
The production boost from a forest is only 20 hammers at the start of the game; that's 20 turns'-worth of working it, plus getting its food bonus. If you have a city with little other production and the forest isn't on a hill, keeping it is often a good idea so that you can build lumber mills when you get to Construction. Forest on grassland (which gives the critical 2 food, plus production) is potentially useful for trading posts. It's a good plan only to cut them down when you need a lump sum of production quickly - for example when building a Wonder or a Settler.
I trade regularly with the other civs, usually swapping one luxury for another, but trading things I do not need for
the rest of the time.
With the way the economy works in BNW, I've tended to find myself preferentially settling duplicate resources I can sell for gold in the early game, as long as my happiness is not too limited.
I readily set up Embassies and Open Borders. I try to maintain Friends with civs, though expect them to stab be in the back at any time. Once available, I try to open Research Agreements as much as possible too, though some Civs always seem to be too broke to do these.
That's quite often because they've already made research agreements with another civ the previous turn - it's gamey, but one option if you have excess cash is to gift them some money (or buy something you need with it, such as a strategic resource) and then sign the agreement.
)........tho I do hope the OP will thank Phil for such a good answer!!! 
in there too, but usually do not prioritise this. Since BNW, I have exploited the heck out of caravans for 
