Start by scraping off the larger pieces of food debris and discarding them into your drip cup or a separate waste bin. Especially stubborn residue may call for more serious cleaning — preheat your griddle as you normally would, then pour a mixture of water and lemon juice onto the cooktop and scrape at the remaining grime. You may also use a griddle stone to scrape the surface when oiled, as long as you remember to scrub in the direction of the grain on your cooking surface to avoid leaving any scratches. You can find a griddle stone at most hardware stores.