Snarzberry, in the game I played last night I tried your early library/national academy gambit, and it worked liked a charm! It kept me competitive at least until the early modern era, and IMHO it was worth the sacrifice of an early wonder or two. I will probably do this from now on in my games.
Someone also mentioned attacking city-states. I did an early attack on a neighboring one, and I believe this did hurt me politically in the long run.
Alas, in last night's game my usual nemesis, Siam, did me in. That 'Father Governs Children' perk I think skews the game badly. My experience has been that if you don't hobble Siam early, by the modern era they become an unbeatable monster. God I hate that little chump Ram!
I've found military wins are quite hard because you get killed by unhappiness as you conquer additional cities (especially above the Prince level). What's the fix here? A lot of happiness improvements? Making the conquered cities vassals instead of annexing them outright?
One more thing. There may be something I'm not kenning about rush-buying. It seems very, very expensive in Civ5, even if you have the Big Ben wonder. As I recall in the early Civs rush buying was cool because you could usually do it a couple turns before normal completion without spending too much money. If it's the same in Civ5, I'm not seeing it.
As Snarz pointed out, NC start is the most consistent opener players agree uppon. It is very, very powerful.
As far as attacking CSs goes. I missed the reply someone said to do this but I will dare saying that they meant to attack a CS to "farm" unit promotions. This means to go with 2-3 melee unit to provide a front and 2-3 siege/ranged. If they really meant to take a CS...then I would have to strongly disagree. Wiping a CS is as harmful as a complete civ wipe in terms of global relationship. Wiping a CS or a civ is really, really harmful to RA success, luxury&open borders income and increases the chances that a bunch of civ talk one another into DoWing you the same turn which can prove to be very harmful to any strat if you don't have a few key chocking points in your empire.
Even when CS DoW me because they are allies of others, I tend to path around them rather than take them at the cost of a few turns to prevent being doomed on diplomacy. Last, whenever I see a CS that has been taken by another civ and have a chance to attack that civ, I will always liberate the CS rather than annex/puppet. This gives me a new bonus, a bunch of extra beakers through scholasticism, sometimes extra happiness esp when I have cultural diplomacy out. It is also good with worldwide diplomacy and costs NO happiness.
Next, I also find siam to be a somewhat painful civ to play against although a way you can help yourself deal with him taking such a huge lead is to bribe other civs to war him or vice versa. This way, you don't get involved in the war but you slow his tech progress, he also gets a few CSs to war him (thus he wont spend gold on taking them for at least the 60 turns it takes to go from -60 to 0 after peace). Another reason why siam is a pain is because of their UU breaking LS rushes down and even remaining a threat to rifles. A good way to counter that though is to build a few pikemens AND to use their upgrade path to rifles as they retain their 100% bonus to mounted. The upgrade from pike to rifle is very costful though so if you weren't going for a warmongering heavy game and didn't go into the professionnal army (honor right side) path, doing this is costful. It still rocks the crap out of Siamese on a renaissance rush though
Again next, total domination got harder in .275 because higher level AIs tend to build many more units from DoWs flying around non stop. Thus I agree that total dom wins are hard. On the other hand though, a wide puppet empire with 1-4 strong&tall cities is very good for a switch to science or diplomatic victory. Happiness issues can be tuned down by proper plans on SPs and by stealing TFP once an AI has it. Last, unless you play multiplayer games and need to field a HUGE army, annexing cities is generally not worth it. My first deity total dom game in .275 was with one city and about 75 puppets. Less of a happiness hit to have puppets, massive gold income so you can purchase units/buildings in your capital, buy more CSs (hell even hard build some late game wonders since you get so much gold you don't really need to build much stuff in capital)
A few SPs that I take when warmongering because they are only "1 sp away" from my regular path are:
Cultural diplomacy (+50% happiness from CSs lux...usually gives me 20-38 happiness depending on CS allying state)
Opening the freedom tree (averages out about 1.5-2 happiness per city since puppets usually fill merchant specialist slots)
And planned economy in the late game but by then the game is often "already won"
Last, rush buying is in fact pricy but when warmongering a lot and mass puppetting, you often have a lot of gold income. Even more if you settle fat peace treaty in your first few wars (don't expect anything the 2nd time you DoW the same civ)
