Started using MTurk four days ago. It's been really great so far! I installed Turkopticon and trying my best to avoid crappy requesters. Any other tips for this newbie?
Stay in contact with requesters, especially if you know you messed up. I mess up once in a while, but work with understanding requesters who approve my work if I reach out to them showing that I put in the effort. Also, if you ever get a reject, contact the requester and ask them why. If they say it was their bad and they can't reverse it, there was a link to a unreject script for requesters in the "Can't Find Good HITs- 9/22" thread on page 30 I believe.
Start a spreadsheet listing surveys you have completed so you can check easily if you've already done surveys that are being reposted.