For everyday cleaning, wipe grates with plain water or water and a few drops of a mild liquid dish detergent. When light residue builds up, remove the grates from the stovetop and soap them in a sink filled with hot, soapy water for about 20 minutes. Rinse and dry the grates thoroughly before replacing them.
Baking soda provides gentle, but abrasive, cleaning power to remove stuck-on foods. An effective cleaning method is to boil water with baking soda in a large pot--big enough to submerge at least one burner grate. Do not fill the pot more than about half full to prevent the water from boiling over. Add the grate directly to the boiling water carefully to avoid splashing hot water out of the pot. Boil the grate for a few minutes to loosen the grime. Remove the grate from the water and allow it to cool. Scrub off any remaining difficult stains.
While it is a harsher, more caustic chemical, ammonia is effective at cleaning burner grates easily. It requires little of the chemical. Simply seal the grates in a garbage bag or resealable storage bag with about 1/4 cup of ammonia. The chemical doesn't need to cover the grates because the fumes clean the grates. Leave the grates overnight in the sealed bag and the next morning the grease and other residue should be loose. Wipe the grates with a sponge to remove any remaining residue. As a warning, carefully open the bag since the escaping fumes are toxic to inhale.
Never mix ammonia with bleach or any product containing bleach. When handling ammonia, wear gloves and do not inhale the fumes; wear a respiratory mask for proper protection. Turn off the stove and oven and wait until the grates are completely cool before cleaning them.