Snakes usually shed in one complete piece. If it retains shed, usually it is because of low humidity in the cage.
Once the snake has shed in one piece, check that both eye caps are on the head part of the shed skin. Check that the cloacal (vent) scales are on the shed and check that the tail tip is on the shed.
If your snake sheds in pieces and skin is left on its body, do not try to peel the skin off unless the shed is still fresh.
If the skin is dried out, place the snake in luke warm water and soak for 30 minutes. Make sure the tub has plenty of ventilation as it will get humid in the tub. You can put a rock or something similar in the tub with the snake so it can rub its body on it to scrape off the remaining skin.
Check the snake after your removed it from the tub to make sure the eye caps, vent scales and tail tip is off.
If the tail tip is retained, it will cause blood flow restrictions to the tail as it dries and eventually your snake will lose the tip of its tail to rot.