I just finished rereading Paco Underhill’s fascinating book, Why We Buy: The Science of Shopping. (Note: the book has been updated, but I read the first edition, so that’s what I’m discussing here.) Underhill invented the “science of shopping,” and he details many ways that retailers can create environments that encourage people to buy.

As I read, I realized that much of his advice could be flipped on its head, to help people resist buying. So often, we operate on habit and impulse. By recognizing the subtle factors that promote shopping, we can turn that information to our advantage if we’re trying to shop wisely.

Many of these tips are very obvious, but as one of my Secrets of Adulthood holds: It’s very important—and surprisingly difficult—to grasp the obvious.

1. Don’t take a basket or cart. People who shop with a basket buy much more than those who don’t use a basket.

2. Don’t linger. How much time you spend in a store is one of the most important factors in determining how much you’ll buy.

3. If you’re a woman, shop with a man. A woman will spend less time in a store when she’s with a man than when she’s by herself, with another woman, or with children.

4. Don’t touch or taste. A lot of impulse buys are triggered by some tactile experience.

5. Be on your guard near the register. Lots of impulse purchases are there to tempt you.

As an under-buyer, I actually have to force myself to buy, so I will use these tips in the reverse—except #5. Under-buyer or over-buyer, no one needs to buy that gimcrack by the register.

How about you? What are some good strategies that have helped you resist impulse buys?

Gretchen Rubin is the author of the #1 New York Times Bestseller, The Happiness Project—an account of the year she spent test-driving the wisdom of the ages, current scientific studies, and lessons from popular culture about how to be happier. On her popular blog, The Happiness Project, she reports on her daily adventures in the pursuit of happiness. Gretchen is also on Facebook and Twitter.