One way to save money is to only go grocery shopping once a week. This is something I just recently incorporated myself.
I remember seeing on Oprah not to long ago, a show where they put some families on a budget. One of the things they did was to bring them to the grocery store and have them buy enough groceries for at least a week. The point was the less you go, the less you will spend.
Seems obvious right? But until recently I was to lazy to think to far ahead when I went to the store. I was going up to 3 times a week. But now I plan out a week of groceries and I am saving money! I figure I'm saving between 50 to 60 dollars a week now.
One of the reasons is I'm not buying as much snacks and junk food. Instead of running out every other day, because my daughter ran out of cookies, she can have whatever else is left in the cabinets. For example my kids like oatmeal, when there's no cookies or other junk left, they'll eat oatmeal for a snack. Which is also better for them anyway!