The easiest way to keep an oven clean is to wipe up spills when they occur and to regularly wash the surface. To clean burnt-on grease from an electric oven, pour 1 cup of ammonia into a glass or ceramic bowl and leave it in the cool oven overnight.
In the morning, wipe the oven clean with a solution of 1 cup ammonia in a pail of water. Wear rubber gloves and follow other safety precautions recommended on the bottle label. Scrub a gas oven with an abrasive cleanser.
Any commercial cleaner is effective for heavily soiled gas or electric oven. These are very caustic, however: follow directions precisely and handle with care. Protect the floor with newspapers; cover thermostats, heating elements, and light bulbs with aluminum foil; and wear rubber gloves.
To clean a microwave oven, cover any spill with a damp paper towel ad turn the oven on High for 10 seconds. When the oven is cool, wipe it clean