Rewards points, cash back, and promotional products are standard marketing ploys to encourage you to spend more. But they’re also so baked into retail that savvy consumers have learned: Don’t spend unless you’re getting something back. As always, though, there are pitfalls to sales promotion and rewards card deals.

Rewards Credit Cards Aren’t Always Rewarding

I realized this when I discovered grocery-store gasoline perks. If I shopped at a particular store and used my rewards credit card, I’d rack up points that could be used to reduce the per-gallon cost of gasoline.

That’s brilliant, except I quickly learned that those points will expire and the only gas station that takes them is completely out of my way. To make it worthwhile, I’d have to plan to need gas on trips in that direction. Complicated.

Frequent-flier programs on airlines are often way more efficient: If you commit to one or two airlines that you really do travel on regularly, you’ll see the miles and free trips add up.

But airlines have expanded the ways to obtain points, including by partnering with credit card companies. Now you can accrue miles every time you shop. Chasing miles and points can be an absolutely effective money saver, but the danger comes with overusing your travel rewards credit card and thinking, I’m earning a free flight every time I shop.

What you’re really doing is racking up debt if you don’t pay off the card every month. So that flight you take with all those miles is hardly free.

Taking Advantage of Sales Promotion Deals

The pitfall is also abundantly clear at cosmetics counters. If you pay attention to the department-store ads and time your makeup buys to promotion deals, you’ll get anything from makeup bags to totes filled with small-size versions of products.

You run into trouble, though, when you find yourself spending too much to get the gift.

There’s often a minimum amount to spend or number of products to buy before you receive the gift. Then you part with more money than you planned to and go home with shades or products that don’t work for you at all. All those free lipsticks end up as clutter.

There’s also that time when you run out of your favorite foundation or just feel like buying a lipstick, but there’s no sales promotion going on. It doesn’t hurt to ask when one might come up, and then wait. I’ve done that and promised a salesperson that I would return.

Making good on that, I ended up with some great eyeliner — and some not-so-great, way-too-expensive facial cleanser that they were clearly giving away because no one was buying it.

If there’s no sales promotion, ask for samples. And if the department store clerk gives you a look, remember, it’s your money. There are other stores and plenty of other brands.

The key to taking advantage of promotion deals is to do some research and avoiding impulse buys. Also use the credit card that gets you the most points or rewards (then pay it off). Plus, you can fire up a browser extension to find out where the deals are.

Plus, some credit card shopping programs have plug-ins that will allow you to activate extra points on your online purchases. It takes a little work, but that’s the difference between saving money and blithely spending.