Start with soap and water with a sponge or rag. If that does not work, use a Scotch-Brite sponge or something similar. This generally takes care of most everyday type spills if taken care of early enough. Tougher stains or scratches can be removed quite simply using ordinary sandpaper. The grade of sandpaper depends on the degree of damage. For light damage, use a smoother sandpaper (the higher the number, the smoother). For more serious issues, use a more course sandpaper. Once the spot or damage is gone, go back over the area with a smoother sandpaper.