Step 1: Sample drink can craft
Edit: In answer to a couple of questions the edges aren't sharp and don't need to be filed or sanded. But if you were making something with corners then that would be a little sharp. So just stick to curved things or cut just the slightest curve on any corners you do have.
Edit: The painted label can easily be removed with 320 grit sandpaper. I haven't tried any other grades.
Update: See http://www.instructables.com/id/Drink-Can-Butterflies/ for an excellent instructable that features a more 3D look and uses permanent markers to add color. It also has good butterfly patterns there to trace. Thanks clintonmc