I found this wonderful cheat sheet on grocery shopping rules from Keeping the Kingdom First. It's short and sweet, but defineity worth trying to put at least a few of these into practice!
1: Do not shop while hungry. This is good common sense.
2: Shop with a list prepared at home (not in the car on the back of an old receipt) and stick to it!
3: Know your target price points. This will vary by region and season. For example, the price to beat on a gallon of milk in my area is currently $2.00, same for a loaf of bread.
4:Use Coupons: combine a coupon with a sale to save the most.
5:Beware of product placement strategies on shelves and endcaps. The best deals are usually high or low on shelves, and not on the endcaps.
6:Eliminate brand loyalty. Be willing to try a variety of brands depending on what is the best value.
7:Find a great deal? Stock up! Since sales only come around every 8-12 weeks, buy enough to last you through the next sale.
8:Get in, get out. Studies have shown the more time you spend inside a store, the more money you will spend. Don't dilly dally!
9:Avoid impulse buys (see number 2). Especially at the checkout stand, where prices are inflated.
10:If possible, leave the kids at home. Enough said.