Very few and usually self policing. They are the obvious rules of common courtesy to other performers. e.g.
Don't enter or leave the club while anyone is performing.
Quiet during all performances.
Respect other peoples point of view and shake their hand not your fist.
Respect all musical instruments and always ask the owners permission before using one. Don't be offended if they say no.
Don't try and bribe the organizers for that extra song. We are of course open to bribery but we come very expensive.