The only real rule is to keep the discussion clean. I can't be op-ing all the time, so if I find out that the room is being used for 'unseemly' discussions, I can only take the room offline.
Enough preaching, here are some useful chat commands:
|/nick my_new_nickname||change your nickname|
|/me action||sends an action (red) message (Example: "/me goes crazy." will show "*my_nickname goes crazy." as an action)|
|/sound sound message||sends a sound and a message (some common sounds are bell, laugh, gong, moo, crash, flush, knock and whistle)|
|/float||floats chat in new resizeable window|
|/quit||leave the chat and disconnect from the server|