To fold aluminum foil properly for cooking and storing food, start by cutting a piece of foil large enough to cover the food completely. For cooking, create a pouch by placing the food in the center of the foil, then fold the edges up around the food, sealing the sides by folding them over multiple times. Ensure there are no gaps to prevent steam from escaping or air from entering. For storing, simply wrap the food tightly in the foil, folding the edges over several times to create a sealed package. Use sharp creases and avoid air pockets to maintain freshness and prevent spoilage.