And your information will get better with age. The longer you keep a price book, the easier it will be to spot trends and bargains. You'll quickly be able to tell the real sales from those that are more headline than savings. But you'll also know when you're looking at a real bargain and be able to make a 'stock up' decision on the spot. Having a menu plan will also help you 'forecast' your usage of an item.
Many shoppers keep a cheap calculator with their book.
It allows them to compare prices on a per unit basis. OK, so it's simple and inexpensive. Thanks again to Lisa for an excellent question. You'll find hundreds of free articles to help you stretcher your day and your budget. There's even a free weekly email newsletter.