Another thing you can do is post a bond with a trusted member so that you can bootstrap off of their reputation. They then hold onto those funds for a specified period of time, and if you turn out to be a scammer, they can pay out any claims from that fund. Thus, people only need to trust the bond holder, not you.
If you're selling to people individually, you can also state that you'll accept using an escrow. One such escrow is
http://btcrow.com/