The George Foreman Grill user manual suggests that the appliance first be cleaned with the plastic spatula included with the grill. The spatula helps remove leftover food residue and fats.
After scraping the grill with the spatula, the user manual suggests using warm soapy water and a soft sponge to clean the grill plate. If the grill plate can be removed from the grill, it can be soaked in warm soapy water instead. It is important to refrain from using abrasive cleaning elements, such as steel wool or metallic scrubbing pads, as they can damage the George Foreman Grill's non-stick surface.
User guides can be found on the George Foreman website. Simply find the appliance page and the link to the user manual is listed under Product Details.