Here's how to avoid the traps.
1. Resist the Smells
The olfactory bombardment starts as soon as the front door swings open. Mouth-watering scents emanate from the bakery and deli, enticing you to buy the more expensive prepared foods, says consumer expert Andrea Woroch. One grocer in New York City even pipes in artificial scents to inspire shoppers to buy more.
2. Forget the End Caps
End caps are the spots at the ends of each aisle, where supermarkets place so-called sale items that aren't always that cheap. They're counting on our preference to avoid heading down an aisle to lead us to grab an end-cap item that seems reasonably priced.
"Don't give in," says Woroch. "Wait until you can comparison shop amidst the appropriate aisle. Better yet, find grocery coupons on your smartphone from sites like CouponSherpa.com, and see if the product on your list is available at a discount."
3. Get Physical
Manufacturers pay big bucks for prime shelving real estate, either at adult eye level or, in the case of products marketed specifically to children, on the lower shelves. Corporations shell out extra cash because they know we're more likely to buy what catches our eye most easily. "Before you grab the first item you see, take a moment to scan the entire shelf and make sure you're truly getting a good deal," says Woroch.
4. Appreciate the Plain Stuff
Product packaging is usually exceptionally bright, featuring plenty of yellows and reds because these colors attract our eyes, says Woroch. Between that and the bright store lights, grocery shopping can lead to migraines.
Fight back against the visual assault, and you'll save money. "Buying generic brands is one of many ways to combat escalating food prices. Before grabbing the first item that attracts your eyes, look for less-gaudy house brands and compare unit prices," says Woroch.
5. Ask for More Cashiers
Stores intentionally understaff checkout lines so customers spend more time standing around near the impulse items that line the corridor leading to the cash registers, says John Tschohl, author of Achieving Excellence Through Customer Service. Items such as lighters, candy, magazines, nail clippers and gum are often found here. "Don't stand for it: Complain to the store manager and ask him or her to open extra checkout lanes," he says.
While you're waiting, don't start picking up things. Instead, think about what you want to accomplish for the day.
"Grocery stories will put regularly priced items on display with a sign. Customers then think because there is a special display that the item must be on sale," says Jack Taylor, professor of retail at Birmingham-Southern College. "They will also price items 'two for $3,' which may not actually be a sale."
Agnes Huff says her husband refused to play the supermarket games. "Every week, Costco changes the location of all the items - so you have to walk back and forth through the store, and I'm sure to encourage you to get stuff you do not need or can use as impulse purchases. My husband complained countless times to management, and to no avail. He finally told them he was not coming back to Costco at all," says Huff.
The key to success: Stay focused.
7. Be Wary of Pairings
"Grocery stores will also put related items together," says Taylor. "For example, they will put chips near the chip dip display. This way, if the customer was only planning to purchase chips, they may see the two together and make an impulse buy. Oftentimes you'll even see these two items on the same display."
Stick to your list.
8. Ignore the Expensive Wines
Supermarkets in states where they are allowed to sell wine often have a glass-front cabinet with $40 and $50 bottles even though few people ever buy them. The reason: Just having it there increases the number $20 and $30 bottles sold, says Patrick Schwerdtfeger, author of Marketing Shortcuts for the Self-Employed. If the selection ranges from $8 to $30, most people will buy something in the middle; say a $17 bottle. But if the selection ranges from $8 to $50, once again, most people will buy something in the middle; say a $24 bottle. "Simply by having a few expensive bottles on display, supermarkets can increase the average purchase by 50% or more. And the best part is that most consumers don't even realize they're behaving differently," says Schwerdtfeger.
Stay within your budget.
9. Don't Buy the Numbers Hype
Signs may say "10 for $10," or "2 for $5," but in most cases, you get the same price if you buy only one, says Carrie Kirby of the blog Frugalistic Mom.
Not every item pictured in store ads is on a large discount -- in fact, sometimes an item pictured in the ad costs more this week than it did last week, she adds.
Deals that offer "seven for $5.50" are designed to confuse shoppers who aren't quick with their mental calculators. The same trick applies to the now popular 10 for $10 game making the supermarket rounds, says Woroch.
Keep your guard up, always, and do your own math.