Buy on sale, and except for cereal, stick to the outside (which includes ice cream at my store!) The sale thing is amusing. I checked the bottom of my reciept from a store since July I "saved $160". I didn't save that, I wouldn't have spent that if if wasn't on sale.
The other thing I try to do is make what I eat. You pay a lot for convience, but sometimes you have to see how much your time is worth. I have a variety of quick foods and slower foods. If you are in the mood for something fast and easy and all you have is stuff that takes time, you'll probably not eat as well!