Making a big purchase? Knowing what you want pays off.

If there’s one thing I suggest that people do before they go shopping for any reasonably expensive item, it’s that they make a list of the features they actually need before they go and stick to that list.

There are several parts to that simple suggestion, though.

First of all, how do you know what features you need? Often, the assumption is that you have to know some things about what the product can do before you can decide which ones you need.

That’s a bad assumption. Not knowing what you want before you go shopping makes you into a target for a salesperson.

The best approach is to sit down and ask yourself why exactly you’re even thinking of making this purchase in the first place.

Why are you thinking of buying that camera? That phone? That washing machine?

You might think the answer is really obvious, but when you actually think about the question for a little bit, it becomes much harder.

For example, you don’t buy a cell phone because you “need” a cell phone. You buy it because you need to communicate in a mobile fashion with people in your life.

Well, then, how do you communicate with those people? By phone call? By text message? By Twitter? What methods do you actually use? Don’t consider what you think you might use someday. Consider what you use right now. How do you carry out that communication?

You might come to the conclusion that you just need a device that enables you to make phone calls and send text messages while you’re out and about. For the vast majority of us, that’s really all we use our cell phones for, other than an occasional “gee whiz” moment. It’s a mistake to pay very much at all for those rare “gee whiz” moments.

To put it simply, the question “what am I really going to use this for?” should lead every buying decision that you make. It’s the key question. If you don’t have an answer for it, you shouldn’t be buying a product. If you do have an answer, make sure it’s a realistic one in your life, meaning that you will actually be using this item because this is a real need for you.

Make a list of those real uses. Then, figure out how those uses translate into actual features on the item you’re considering buying. Most of the time, you’ll find that your actual uses translate into a pretty bare bones model, which means you’ll be saving a lot of money.

This post is part of a yearlong series called “365 Ways to Live Cheap (Revisited),” in which I’m revisiting the entries from my book “365 Ways to Live Cheap,” which is available at Amazon and at bookstores everywhere.