The easiest way to maintain your grill is to clean it after every use, but often when the food is removed you're busy eating and socializing -- cleaning the grill becomes a low priority. If you've let some baked-on grime sit on the grill, you can clean it quickly and easily with foil by using the grill's heat to your advantage.
Make sure the grill is cold (and turned off, if it's gas-powered).
Cut two lengths of aluminum foil to measure the width of your grill. Cover the racks with the foil and tuck down the edges. Make sure you cover the racks completely and that the shiny side of the foil faces the racks.
Fire up the grill, close the lid and let the heat do the work. You will see billows of white smoke coming from your grill, but don't get worried -- these are caused by the cleaning process. Leave the heat on for about 15 minutes, then turn the grill off and let it cool.
Open the lid once the grill is cool, remove the aluminum foil and bunch it into a ball with your hands. Rub the foil ball across the racks to remove any remaining residue and baked-on food.
Rinse the racks with plain water or wipe them down with a wet sponge and leave them to air dry.