it takes a lot of knowledge to get into the top ranks online. i've been in the top 10 on both systems (psn anarak, xbl gamertag= amazingrayson), and you've gotta know how to defend against rushers, tech really fast, and always try to expand expand expand.
don't get caught in the trap of playing only as an easy civ like a lot of players do, lots of ppl only choose Zulu or China, which is like civ with training wheels..
go to forums.2kgames.com and click on the civ rev section and look at the posted strategies there. this message board will teach you everything you need to know and more about the game...
but the biggest advice i always give to multiplayer newcomers is that you shouldn't work your cities on balanced at the start, put both workers on forests and pump out a couple warriors, then grow your city back to three population, then consider working balanced or tech. you've gotta settle a lot of cities as the game goes on. against the ai you can get away with only 3-5 cities, but online you need at least five, preferably 7-10 or even more.
