In the battle of the budget, the supermarket is a psychological war zone.

The aroma of fried chicken greets you at the door, and the irresistible scent of fresh bread wafts from the bakery. Brightly colored fruits and vegetables beckon nearby.

"It's like aromatherapy," said Phil Lempert, the Internet's Supermarket Guru. "And they're all intended to put you in the mood to buy."

It's no wonder the average family of four spends more than $700 a month on groceries, according to the U.S. Department of Labor.

But even in a setting where everything has been tweaked to appeal to your shopping instincts, you can trim your food bills if you stick to a plan.

"If you go in and browse, to see what you like, you'll come out with a heck of a lot more than you intended to spend," said marketing professor Daniel Howard of the Cox School of Business at Southern Methodist University.

"But if you go in with a specific list and say this is what I'm going to buy, you'll be OK."

That's a challenge, though, because supermarkets are designed to appeal to the consumer's senses, which seem directly wired to the wallet, he said.

Even beyond the sights and smells, the supermarket is something of a psychology lab.

The products you buy most – milk, eggs, meat – are placed as far as possible from the store's entrance, so the shopper passes hundreds of products to pick up a pound of ground chuck. That's a lot of opportunity for an impulse buy.

Other popular items are placed in the middle of an aisle for the same reason, stretching the time spent shopping.

"They learned that lesson from Las Vegas – the longer they keep you in the casino, the more you spend," he said.

There's even science at work in arranging the shelves.

People are comfortable looking straight ahead, rather than up or down. So stores stock higher profit items at eye level, and manufacturers pay for that placement.

"The golden rule of supermarket retailing is 'Eye level is buy level,'" Dr. Howard said. "If you're buying something at eye level, you can be sure that isn't the best deal."

Items aimed at kids are a bit lower. And what a child sees, a child wants.

Bulk items and store brands are on the lowest shelves. They're mostly ignored.

"People don't like to bend over," Dr. Howard said. "They don't like to buy from the bottom shelf. But that's where the best buys per ounce are."

Over the years, shoppers grew conditioned to finding sale items at end-of-the-aisle displays, Mr. Lempert said, a fact not lost on the supermarkets.

Now, perhaps only half of the end displays hold sale items. But that doesn't stop shoppers.

"Stores just put things on display at the end of the aisle and people buy them," Dr. Howard said. "Placement is enough to persuade them the price has been reduced, whether or not it has."

And when stores price items at "three for $5," or "10 for $10," shoppers believe it.

"There are many who think they need to buy those quantities to get that deal," he said.

Not so. Buy the number you want, and bring a pocket calculator if you're unsure of the per-unit price.

There are other ways to keep from overbuying, too.

"Go in with a specific list, buy and get out," Dr. Howard recommended.

Mr. Lempert fights the grocers' strategy by ignoring the path they lay out for you.

"I go straight through the center of the store, where the unemotional boxes and cans and jars are," he said. "That way, you don't get all those senses going that make you want to shop more."

Finally, he said, use the store's frequent shopping card. Some shoppers worry that computers track every purchase they make and gather personal information.

Mr. Lempert doesn't buy it.

Use the store's circular to build your shopping list and the shopping card to take advantage of 2-for-1 deals and other specials, Mr. Lempert said.

"It's low-hanging fruit, like using coupons," he said.

"And it saves you money."

Supermarket Guru Phil Lempert offers two suggestions:

"People love berries, but this time of year you might spend $4 or $5 for four ounces," Mr. Lempert said. "Go to frozen foods instead, and you'll find 16-ounce packages for $1.50 to $2. And those berries were picked at their peak and frozen, so they have more flavor and better nutrition."

Seafood: Avoid the store's seafood, most of which was frozen and thawed, and buy from the freezer instead. It will have better texture, he said, and will cost up to 40 percent less.