We currently don't have any outlined rules for our main chat room. There hasn't been any behavior that would prompt the need for rules, but it would be a good idea to have something to refer to for new users.
Other than "be nice", there aren't really any rules in the chat.stackexchange FAQ. Mathematics.SE has a nice post outlining chat etiquette, but a lot of those wouldn't apply to us.
To those familiar with chat, what sort of guidelines would you like to see laid out?
Once we have a collective agreement, I'll make a community wiki post that we can permanently pin in the chat room.
To those unfamiliar with chat: stop being a stranger and join us!