Make sure you pick up a cheap rim to practice on. Those are good fr bending rims as well as braking a few fingers while learning unless you are above the curve.
I personally use a NO-Mar Tire Changer and it is impossible to bend a rim or scratch if used properly. Plus they offer a lifetime warranty on all the parts that contact your rim during the change. At least with a NO-Mar you can feel exactly how much pressure is being applied to your rim through out the entire change.