Wonder Square is for games, birthdays, newbies and fun.
General Chat is obviously for conversation of a general nature.
EoEo is serious business. No spam or flaming. Post on topic or get out.
The Lounge is fun media stuff.
The gaming forums are self-explanatory.

Be nice, don't call people names, don't be a jerk, do participate in forum events, do make welcoming posts in newbie threads and you'll be alright. Poke around and see what forums you want to talk in, and stay away from The Thing In The Attic.