Saving money using a coupon on a single item is great. But it's only a small part of what is possible with couponing. Timing is the key to significantly cutting your grocery bill. By using coupons at the right time, and in the right combinations, you can save so much more.
Shop the sales. Shopping the sales will save you more money than using coupons alone. Peruse the ads you see in newspaper circulars or online and plan your shopping list based on what's on sale that week, and not necessarily what you want.
Combine sales and coupons. This is where it gets interesting. As you're watching for sales, also see which sale items you also have coupons for. That's double savings! You get the coupon deal on a price that is now lower, which means you spend even less overall.
The beauty of BOGO. It gets even better when you combine buy one get one free (BOGO) deals. That's when you have a BOGO coupon for an item that the store is also running a BOGO sale on so you get two free ones. Another way to double up is to use one BOGO coupon from the store in combination with a BOGO free coupon from the manufacturer. Most stores allow you to "stack" coupons in this way, but not necessarily all, so be sure to ask first.