Clean your tin carefully and completely. This is especially important if you are reusing a tin can that food came in. Be careful as these can have sharp edges.
Draw your design in dots on the tin. If you prefer, you can draw it on a piece of paper and tape the paper to your tin. Permanent markers work well for this part of the project.
Lay your tin on a piece of wood or other surface that won't suffer damage when it is hit. Lay a rolled towel on either side of the can to prevent it from rolling.
Place your nail on one of the dots in your design and tap the nail with the hammer. Try not to punch completely through the can with the nail, although you do not have to start over if you accidentally do.
Continue to punch out your design by placing and tapping your nail on each dot.
Remove the paper from your design once it is complete. If you didn't use paper, simply clean off any marker still showing with a bit of acetone, which can be found in most fingernail polish removers. Douse the cotton ball in the polish remover and rub it gently over the mark. The marker should be removed from the tin.