As above, mild heat application will be helpful. Start at a corner and peel slowly. Residue can sometimes be removed by rubbing a piece of clear packing tape onto it and using the tape to peel it off. Sometimes you can "roll" the residue off with your thumb. Otherwise citrus cleaners will often turn the residue to a gummy "snot" which can be rubbed off. There is a line of products called "Goo-Gone" which may also help. http://www.googone.com/ I've never used the 3M adhesive remover but have heard of it being highly spoken of. Mineral spirits and alcohol are also sometimes effective.