The interwebs has gone peplum crazy. I first noticed it on Tina Fey at the Oscars, but now I can't browse without stumbling across it repeatedly.
Start with a shirt that's too big for you. You want the shirt to be long and swing freely around the bottom edge. (My shirt was about two sizes too big. I found this beauty at the thrift store for $4. The beautiful polka dot fabric was in such good condition that I couldn't pass it up!)