Make a LIST and check it TWICE!
One of the easiest things you can do to say some cash is to make a list before you go shopping and stick to it. Without a list you will buy items that you simply do not need. Even worse you may forget to purchase the actual item you came to the store for in the first place.
This is not just for grocery shopping but any shopping or trip you need to make such as stops you need to make while your out driving. Then stick to it too stop yourself from buying impulse items that you don't need and making stops you hadn't planned to make where you will spend even more money.
Too make it more efficient plan your route as well. Planning your route allows you to take the shortest trip possible and not have to double back to hit stops you missed which again saves you time and money.