As I've noted before, when it comes to grocery shopping, Brian and I don't exactly play by the rules. Most money-saving articles recommend that you make just one big trip to the grocery store each week, or even each month, to stock up on everything you need. The idea is that by limiting the number of trips you make to the store, you reduce the number of impulse purchases you can (or, as some of them claim, invariably will) make.
The problem with this is that if you make only one shopping trip a week, you have to buy everything you need that week at one store. And when you do this, you can't possibly be getting the lowest price on everything, because every store has better prices on some items than others. So our system involves stopping by multiple stores over the course of a week or a month, whenever we happen to be in the area, to buy the items that are the best deals at that particular store.
What I haven't talked about all that much is how we keep track of all those prices at all those different stores, so we know what to get where. The answer is, we write them down in a price book: a little loose-leaf notebook small enough to tuck in my purse, with a page devoted to each item we buy regularly, listing the prices at all the stores where we habitually shop. If we're in need of anything and not sure where to buy it, all we have to do is check the price book to see where we can get it cheapest (or find the cheapest regular price and then wait for a sale price that's even less). Keeping a price book is a strategy we learned from Amy Dacyczyn of The Tightwad Gazette (all hail the Frugal Zealot!), and it's probably the single most useful tool we have for keeping our grocery bill in check.
In my latest Money Crashers article, I go into more details about price books, their benefits, and how to make your own. I discuss the different ways to do it (a notebook like ours, an Excel spreadsheet, a smartphone app) and the pros and cons of each, and then I outline some strategies for getting the most benefit out of your price book.
Check it out here: How to Make a Grocery Price Book to Save at the Supermarket