One hotly debated topic about keeping glass-top stoves in good shape is whether to use a razor or sharp scraper to assist in removing tough, grungy food stains. Reading the many public discussion forums about glass-top stoves will probably only confuse you more. Some people say you're risking an expensive product by bringing a sharp object near delicate glass. Others say if you use it on the right stain, such as burnt cheese or other residue, and you're very careful, a scraper will absolutely help keep the stove clean.
Appliance manufacturers do recommend purchasing a special scraper, which comes in a kit with a stove-top cleaner and soft cleaning pads. Here's what to do: Add a liberal amount of liquid cleaner to the area affected and use the scraper to lift burnt-on debris. Using some pressure, move in a forward and backward motion with the cutting edge of the knife. The cutting edge should be held as flat against the glass as possible, while still maintaining contact. Do not use the corner of the scraper or razor blade, as it can scratch the glass top.