1. Eye Candy

Most shoppers are fully aware that supermarkets deliberately put candy and magazines at the checkout counters, where they can easily tempt bored, cranky and hungry shoppers. But it doesn't stop there. Throughout the store, supermarkets strategically arrange products on the shelves in a way that makes you buy more.

Take, for example, the cereal aisle -- it's usually located directly across from the candy section. "It's a mother's greatest nightmare," Lempert says. "You'll find breakfast cereals on one side and candy on the other." Why? So kids can check out the candy while Mom is filling up the cart with cereal -- a must-buy on most shopping trips. Likewise, sugary kids' cereals are always on the lower shelves, at a child's eye level and within reach of little arms.

What you can do: If possible, leave the children at home so you don't end up buying too much junk food. Otherwise, distract them. Kimberly Danger, founder of Mommysavers.com, usually "bribes" her two kids with lollipops while shopping. "It keeps them occupied and they're not distracted by the candy," she says.