Here's what I do:

If it's just a small piece I will wet a q-tip with warm water and then rub it over the dry skin several times. Then gently, pull the skin up, it should come right off. If it doesn't come off easily, wed it a little more.

If it's a larger piece or an incomplete shed, take several paper towels and wet them (completely moist, but not soaking/dripping) with warm water. I put those in a small tupperware container with holes drilled so it can breathe. Then put the snake in there and close it up. I leave them in there for 30-45 minutes and let the humidity soak the skin. Remove the snake and gently peel away the pieces of skin. They should come off pretty easily. Hope this helps.