1.No flaming. Saying "Dallas sucks" (Or "NYG Blows" or anything along those lines) is perfectly fine (and in fact, encouraged) - but saying something offensive to a user is considered flaming and bannable.
2.Don't make a thread saying "My team rocks" or "Your team sucks" without content, an article, or something to discuss.
3.Support Threads - If you hate the team, don't even go in these threads. Respect other fans' support threads, and they'll respect yours.