Clear, cold water
A sponge or rag
Brand new straight razor blades
Make sure you are careful!
Using the sponge or rag, thoroughly wet the decal (sticker) as well as the glass completely surrounding it, with the warm soapy water. Let it sit for about three to five minutes, soaking.
Rewet the area with the warm soapy water. Holding the razorblade at a 45° angle and beginning with one of the upper corners, carefully slide the razor blade under the corner of the sticker, gently prying upwards as you continue to slide the blade under.
Be careful not to apply excess pressure to the razor, as it can slip and slice into your hand, forearm, or the glass. With your other hand, gently pull the free edge.
Continue sliding the blade under the decal or sticker until you have successfully freed the top of it completely lengthwise. Still holding onto the free top edge with your other hand, continue sliding the blade downwards, working towards the nearest lower edge of the sticker.
By now you should have three quarters of the sticker free. Continue pulling with your free hand and wedging the razor underneath the sticker until it is completely free.
Rewet the area. Using a brand new razor blade, holding it again at a 45° angle gently scrape away any glue residue left behind from the sticker. Again, be careful not to apply too much excess pressure to avoid gouging the glass or losing control and cutting yourself.
Once the sticker and all of its residual glue has been removed, thoroughly rinse the area with the cold clean water to remove any soap residue. Dry the area thoroughly with paper towels.