Save all your grocery receipts for one month. Include receipts from food purchases made at convenience stores, as well. Keep all your receipts in a single location, and after one month, get them out and take a look.
Divide purchases on each receipt into categories, marking each category with a different color higlighter marker or a special symbol. For example, you might draw a green line through produce items, a pink line through meat products, a blue line through dairy products, a star beside junk food items, a heart beside household products, etc. Select categories based on what you buy and what's important to you.
Make a master list of all the different categories of groceries you buy, and under each heading write the total amount you've spent on that category, adding all receipts collected over the one-month period. Evaluate the data. Are you spending more on junk food than on healthy food? Are convenience foods eating away your grocery dollars? Seeing where you're spending will help you to better prioritize, plan, and balance your family's food budget.
Start saving those receipts right away and see for yourself how much you'll discover and learn about budgeting your grocery dollars. Happy savings!