It can really depend on the game. Sometimes you'll just get an AI that wants you dead, polite or otherwise. But yes, I agree that keeping them happy is your best defense, and alliances are key. It helps if you can provide your own iron, but sometimes that can be a tall order.
A second suggestion I would make is selecting a map with 70% ocean, as resources/luxs/bonuses tend to be more clustered and you'll have a better chance at a landing a capital near some goodies.
I've done two successful OCCs, both ended up as 20K wins. They were vastly different experiences, despite similar map selection and difficulty level. I actually came close to being destroyed in a regent game, but a clever alliance with the Persians had him eliminate all the other civs on my continent, leaving only him (friendly to me because of all our deals). However, it was harrowing because I was in the middle of everything.
The other game, monarch difficulty, I was on the end of a long, stringy continent with only one civ sharing a border. They were benign towards me the whole game and through several alliances kept the bad ones at bay. I even had time in between a few of the wonders to pump out a bunch of knights (iron popped up on the hill underneith my capital, horses were on the fringe until my neighbor's culture expanded late-game and took it

) and went on an offensive to clear out a couple of junk cities on the north end of the continent that belonged to off-continent rivals.
So I guess to sum everything up, the best thing you can do for yourself is get a good start and keep a couple of really good friends. If the first civ you meet is already "annoyed" with you, its probably going to be a rough game. Also, without three AA wonders, I'd say forget a win before retirement. With proper management, its usually pretty easy to score the Colossus, Oracle, GLib, and Gardens with a coastal start. Once you hit the MA, I'd say republic is the best bet, since monarchy will have such a low unit support for only one city. I think I managed to get the sistine chapel and shake's in both games, Bach's in the monarchy one. Leo's and Sun Tzu's are really useless for OCCs, IMO. I think in both games I lost Copernicus to wonder cascades and fell hoplessly behind in techs to get anything after that
Funniest thing; I just tried a 20K with the Aztecs, ended up with 7 great wonders and four small wonders all in Tenochtitlan, and finished in the exact same year as my monarch OCC with the Egyptians (with only six gws and no sws)

The major difference was the OCC only took about 6 hours of my time, the Aztec game probably 13 or 14 hours.