Brush your grill grates after every use (inspect for wire brush bristles before cooking), and thoroughly clean them every couple of months, depending on grill usage. And twice a year, you should give your grill a thorough cleaning, which helps it cook better and last longer. The basic process is the same for gas or charcoal grills; charcoal grills just have fewer parts.
Clean the bottom of the grill with a soapy sponge. Once all the chunks are gone, scrub the bottom with a sponge or scouring pad and soapy water to remove any built up grease or grime. Lots of drippings and food scraps tend to build up under the burners of the grill. Pay close attention to this area and clean it as much as possible to avoid corrosion.