Misusing the garbage disposal is the most common cause of broken or clogged machines. Never put any non-biodegradable items down the garbage disposal, including glass, metal, or plastic. Most soft, biodegradable materials are OK, as are some hard, biodegradable materials such as eggshells, ice, and small bones. Avoid putting tough or stringy food items such as corn husks, potato peels, or celery stalks through the disposal, and always run cold water while you are running the machine, as this can prevent cooking grease from congealing within the pipes.