First things first, download Gimpshop so you can practice along with the following directions! Gimpshop is the same program we used to give a picture a transparent background the other week, so you may have already downloaded it. If not, go get it now! It's like photoshop, but free! And... it works on Macs and PCs!
You can download this tutorial as a PDF by clicking this picture!
Note: This tutorial is hosted on Google Docs. To save it from there, just open the file and click File > Download to save onto your computer!