The biggest target for saving is in the food and grocery area. The reason is simple. We spend about 20% of our money on food. We're making decisions about buying food all the time.
A pricebook is an invaluable tool. It's a simple listing of items that you purchase regularly (i.e. milk, bread, ground beef, etc) and the lowest price that you've paid for it recently. The most effective pricebook includes one sheet for each item with the store name, date and low price recorded.
Since loss leader sale items appear on the front and back of sales circulars, I can create the price book at home without even going to the store!
Taking the pricebook to the store allows us to quickly identify real sales. That gives us the opportunity to stock-up on an item when the price is right.