Using the knife, make a hole in the corner of the guitar pick, not too close to the edge or where you will be cutting the heart shape. Just move the pick around or back and forth while pushing down with the knife. It may take awhile if you are using a heavy gauge pick.

Cut out the heart shape from the top. If you don't know how to do that, it's just a rounded indent at the very top of the pick. Don't worry about the shape being perfect, you can sand it into shape using the nail file. You can draw an outline of where you want to cut on the pick, but pen and pencil don't work, and sharpie might leave a black line.

Sand that baby down! It's completely optional, though, but it helps the grip on the pick, and it's a good idea to at least sand the top so it isn't sharp. Also, if you're using a clear pick, it makes it look a little like sea glass, which I love.