You are only allowed to have a maximum of 2 topics active at any given moment. This generally means 1 buying and 1 selling topic. There is no need to have a bunch of different topics. If you have a wide variety of items to buy/sell, then make 1 topic to buy/sell them all
Do not bump your own topic if the last reply was made within 8 hours. As well, only bump your own topic. Do not bump other people's topics
Only post if you have something constructive to say. If someone's selling an item, you can inquire about the price, make offers, or anything else that's relevant. Do not post irrelevant or unneeded content in someone's thread.