Everything about the supermarket is designed to prolong your trip. Meat and milk are at the back of the store because they’re often necessary purchases, and that placement forces shoppers to wander past more profitable perishables. And coffee bars and piped-in music soothe and distract you from the nuisance of shopping. But they could also make you linger longer and therefore spend more.

Sometimes such tactics can backfire. Displays that jut into an aisle shout “low price” and get shoppers to slow down, but they also snarl traffic. Overall, 16 percent of survey respondents complained about congested aisles. At Wal-Mart, the biggest offender, that figure was 35 percent.

Retailers are no doubt aware of the criticisms, and Food Lion decided to address them. The North Carolina-based chain is experimenting with markets called Bloom, in which milk, bread, eggs, and prepared foods are at the front of the store; shelves are lower; frozen foods are near the checkout; and personal-care products are near the pharmacy. The Bloom concept is a no-brainer, but so far we haven’t seen copycats.

One store where you’ll never trip over merchandise is Amazon.com (see Amazon.com for groceries). If you choose a more traditional venue, follow these tips:

• Understand the “high-low” game. Most chains sell some items at or below cost and mark up others to erase the shortfall. Most types of stores, including gas stations and convenience stores, discount frequent purchases such as milk and eggs. These “loss leaders” are featured in weekly supermarket flyers, and you’d be hard-pressed to find them cheaper even at warehouse clubs.
  
  You can time purchases of cereal, juice, foil, paper towels, and other staples to avoid paying full price. Products go on sale at predictable intervals that differ store by store. Learn the pattern by perusing store flyers, then stock up and save.
  
  
• Watch out for misleading messages. Ambiguous wording and incorrect images in circulars can cause confusion. We saw a picture of chicken legs and thighs in one flyer, though only legs were on sale.
  
  
• Beware of sneaky signs. Signs touting 10 cans of soup for $10, for example, may not require you to buy all 10 cans to get the discount. Stores are just planting a number in your head, hoping you’ll buy a lot.
  
  
• Pay attention to nutrition labels, not product placement. Shoppers tend to judge the healthfulness of certain products by the ­company they keep, says Brian Wansink, director of the Cornell University Food and Brand Lab. Placing salsa and chips with produce instead of snacks imparts a “health halo,” making you more likely to buy them.
  
  
• Assess the “fourth wall.” That’s industry-speak for the front of the store, home to highly profitable coin sorters, vending machines, lottery tickets, and seasonal merchandise. The mix usually includes both high- and low-priced items. At an A&P, we saw signs for a sale on the chain’s brand of charcoal, but alongside was an even bigger display of Kingsford, a national brand. It was selling for full price, or 40 percent more than the A&P charcoal.
  
  
• Check out the checkout. Seven percent of survey respondents said that scanners got the total wrong, and no chain was especially accurate or inaccurate. Report a pattern of errors to the Federal Trade Commission (www.ftc.gov), your state attorney general, or your local consumer-affairs office.

The FTC recommends that retailers offer overcharged consumers a reward, and some do. Our reporter received a free can of fruit from Publix when he explained that the shelf-tag price was lower than the scanned price.