Keep it civil, do not flame or bait other users. If you notice anything illegal or inappropriate being discussed, contact an administrator or moderator.
If you do, have some god damned tact about what you're saying.
If you try to spark a comment war/are just to inept to know how to comment without sparking a comment war, do not do it.
Also, if you're going to be one of those chucklefucks who occasionally visit a Yuri/Futa image or something trying to tell people how it's morally wrong, don't even do it and just leave the website.