Discover Your Stock Up Price. It is important to learn what a 'good' price is for an item, and then set a price goal for individual items.
For example, I have found that I will not pay more than $1.69 for milk. I can price match the Smith's add at Walmart instead of paying the labeled price of $2.06. Just spending 30-60 cents less on milk saves a little from my grocery bill each month. This same idea should be used on all your groceries- find the low price & stick with it.
How? I recomend starting with the top 10 items that you use every week. Make a list of the items, then keep track of how much you spend on that item. It may take a few months before you see the trends in sales and the rock bottom price, but you can slowly learn how much you can expect to pay for each item.
Why? Once you have developed a 'stock up price' for an item, you can be a smarter shopper. This will help you set a realistic budget on your groceries. If you only buy items at their lowest price, you will see a significant decrease in the amount you spend each month.
You find more posts about building a stockpile & stock up prices by following the links or looking under the frugal tips tab.