Start out by warming the entire area of the sticker and warm a little of the surrounding area also. Once the sticker is warm to the touch, then beginning at one corner, carefully focus the heat on that area while attempting to peel back the corner of the sticker. Work slowly by keeping light tension on the sticker while heating the area in front of where you are pulling. What you are doing is softening the adhesive which holds the sticker in place. The newer the sticker is, the better the process works but I have successfully removed very old stickers and I have even successfully removed mailing labels from old magazines using this method.