How to, with free printable pdf designs, check out Wild Olive. She mentions a specific magnetic tape, but office supply stores sell thin printable magnetic paper that you could cut to size and use instead ... just an idea. (BTW ... i make my own magnetic bookmarks ... my kids have a tendency to throw my books around and regular ones slip right out waaaaaay too often!!)
Do you a tutorial that you found and want to share, or something that you would like to know how to do? Shoot me an email (found on my profile page) and I'll get it up on Craftivision ASAP!