Frequently in this space, we will consult a different entry in the 1987 book The Modern Man’s Guide to Life to see how the advice therein has aged. On Monday, we discussed dealing with drunk friends; today, we’ll explore the foreign world of shopping.

Even if you loathe shopping, you’re going to have to bite the bullet (and buy it first) sometimes. And sometimes the things you’re buying are big things. So, natch, the Modern Man’s Guide to Life has a few very helpful pointers that apply to a lot of different scenarios.

When you think it’s time to throw down on something significant:

Avoid making a major purchase on impulse. A car, a new roof, an expensive insurance package are all things that should be carefully researched before you commit. Do comparison shopping—you’ll always be surprised—and remember to figure terms and financing charges as part of the purchase price.

In other words, don’t run into the first condo you’re looking at, do a spin around the living room, and grab the realtor by the shoulders, kiss her on the mouth, and yell, “I’ll take it!” without doing your due diligence. I mean, duh. But what about the things that don’t cost thousands of dollars, like groceries and day-to-day necessities? There’s a recurring theme: Plan ahead, watch for sales, buy in bulk when possible to save money, and this ever-important piece of advice:

Never shop for food when you’re hungry, or without a list.

That is a word of advice that has withstood the test of time. (True Detective: “Never do anything out of hunger. Not even eating.”) It’s how you avoid going home with a cart full of Flamin’ Hot Cheetos and frozen TGI Friday’s loaded potato skins. (Unless that’s your thing). But really, what all of this boils down to—whether you’re buying a new car or a week’s worth of groceries—is to go in with a plan. That way you avoid any surprises, and you avoid getting screwed over or, more to the point, screwing yourself over.