Over the period that I've lived at my current place (both times, technically), we've refined most issues down to a simple set of rules to eliminate drama. For a long while, it was only two rules... but we've found reason (premptively) to add new rules as situations arise. Amazingly, I find this list to be a little funny, a little pathetic, yet amazingly effective. Let the world be the judge... ;)
The Rules @ Casa del Pecado:
Rule #1: No sex between roommates.
Rule #2: No sex with a roommate's boyfriend/fuckbuddy/partner/etc.
Rule #3: No sex with a roommate's family members.
Later added: ...without the roommate's permission. ;)
Rule #4: No sex with a potential roommate in an attempt to prempt rule #1.
(as we're looking for a roommate, and a potential has a cute name, Rule #4 was just created a few minutes ago ;))
It's amazing how much drama these rules eliminate when living in gay-slanted household. :)