With three children under four, going to the store is a major event and I hate having to go more than once a week because I forgot something or we ran out of something before shopping day. The "Top Shelf Rule" has helped out tremendously.
Buy one extra of everything nonperishable that your family uses regularly (ketchup, rice mix, soup, cooking spray, ziploc bags, etc.) and devote your top pantry shelf to just these items. The top shelf rule is that no one in the family is allowed to take something down from the top shelf without first writing it on the grocery list. This way, we never run out of things before grocery day. It has worked so well, that I have started a "top shelf" with my cleaning supplies too.
ThriftyFun is one of the longest running frugal living communities on the Internet. These are archives of older discussions.
Making and using a grocery list will help you buy only necessities and/or sale items so will help you save money.