There is another alternative, and that is being patient. In the vast vast, majority of cases, if you apply only the slightest force to pull the sticker off, and you apply it evenly along the axis (eg, not from a single corner, but evenly along an edge) you can literally just remove the sticker. Of course though, if you are too late and someone has already removed the sticker leaving behind residue, yes, these methods work great.