Covering the pot with aluminium foil protects the dish from excessive heat. You could also reduce the heat.
Another way to prevent your food from burning is to use a nonstick pot. In the absence of a nonstick pot, preheat oil in the pan before adding food. Any pan, regardless of the material, should be treated with oil before you begin the cooking process. Oil seeps into the pores of the metal when exposed to high temperatures, creating a sort of nonstick coating.
