Water and a bit of scrubbing should be adequate for every day messes on glass stove tops. For cooked-on food, it's best to use a specialty glass-top stove cleaner such as Weiman cook top cleaner and polish or Cerama Bryte.
Specialty cook top cleaners are effective at removing baked on stains without damaging the delicate glass surface. Many cleaners are sold with a kit that includes a plastic scraper for additional help removing difficult stains. If a stain remains after cleaning, repeat the process several more times. The best method for keeping a glass cook top clean is to immediately wipe up any messes while cooking.