These are a few of the basic commands you will need:
pub <message> - Speak on the Public channel.
say <message> - Talk to people in the room with you.
:<action> - Pose an action.
OOC <message> - When IC, an OOC aside. Use sparingly!
OOC :<action> - When IC, pose OOCly. Use sparingly!
WHO - See a list of connected players.
EWHO - See a list of connected players in your empire.
page <player>=<message> - Send a private message to a player.