Soak the glass in hot water for 20 minutes. This will loosen the label and soften the adhesive quality of the label glue.
Scrape the label with a razor. Start at one edge, and scrape without scratching the glass. Pull and scrape until most of the label and glue have been removed.
Scrub the label with a nylon scrubber, which will scrub away the adhesive without scratching the glass.
Rub vegetable oil over any remaining label glue and leave it overnight. The oil will reduce the adhesive quality of the glue.
Scrub once more with the nylon scrubber, then rinse with hot water to wash away any remaining residue.