Be Fonz cool is the golden rule. That is, don't flagrantly flame or hate people, keep content PG13-[i]ish[/i] (while I've never seen a barrier on graphic violence, gratuitous descriptions of sexual organs or acts is not allowed), and uhh... No that's about it really. The big no no's are don't commit hate speech against individual people (characters or concepts are fine) and don't describe sexual acts or organs except through metaphor and so on.

ex: If two characters have sex, fade to black. If a character is naked, don't describe the naughty bits. So on and so forth.