DON'T: Insult someone's ad, price or what they're selling. If you don't like something, don't buy it. If you like something but it's too expensive, don't buy it. Vote with your wallet.
DON'T: Have discussions that are NOT related to the product. (If it's related to the product, why they're selling, etc, that's cool.)
DO: Keep general chatter in ads to a minimum.
(More to come, probably ?)
If you wanna suggest any rules, please post them in the "Site Feedback" section of the site. I'd like to keep this thread pretty clean.