You can write down things you need when you think of them. Check your kitchen cabinets and refrigerator as you make your list. Organize the list the same way the grocery store sections are laid out. You will save time and avoid forgetting items when you shop. Look at the newspaper and ads for sales and coupons.
Hungry people tend to buy more food than they planned on.
Know the current prices of the foods you buy most often. Buy the amount of food that fits your family's needs and your storage space. Buy larger sizes of items that won't spoil. It may be cheaper. Buy the quality and size of food that fits how you will use it.