Whatever you do, don't get anything with a trillion sequins or that shit, it looks tacky. Don't get a white dress either, I hate those girls who look like they're ready to get married rather than just go to a prom.
I went on that site the person above posted and I think if you're going for a longer dress a mermaid hem would look nice on you, like
this or
this. If you're going for a shorter, well, I don't think you should.