Some tips my sister was telling me (and they sounded VERY smart!)
1. Look at your local grocery ads for the week and plan your meals around what is on sale!
2. Budget! And stay on budget!
3. Shop every week, but ONLY once a week. If you forgot something you need, too bad, don't go get it unless it is vital.
4. Shopping list. Go through cupboards and look at what you can have and use. Keep the list on your refridgerator so that the minute you run out of something (like ketchup or salad dressing) you can put it on your list so you don't forget and end up making more than 1 trip a week.
5. Keep coupons to a minimum. If you need something, look for a coupon for that thing. Don't buy something just because you have a coupon for it! (Thanks Shalyse!)