The KoolStop Beadjack above is a lifesaver. I have used this on older Schwinn S7's w/Kenda tires, and a skinny tire on a 26" MTB rim. On tight rim/tire combos it is very easy to pinch the tube using levers and the bead jack eliminates this. I have used them on wider tires also.
What tires and rims do you have. Maybe somebody could reccomend a better tire.