No one ever wants to spend too much or feel exploited after a purchase. It's an especially painful prospect in these lean economic times.

Few of us can afford to be burned by pricey add-ons and deals that really were too good to be true. Yet, with many retail chains struggling, you may be more likely now to face dubious come-ons, as stores turn to more imaginative strategies to get you to buy.

Here are things to stay alert for, whether you're shopping for toothpaste, a Toyota or a flat-screen TV.

Deceptive price markers. Many groceries and drugstores now use bright colors or symbols to highlight prices that suggest that the products are on sale, when the price is actually just the usual nonsale one. Some stores also highlight their own generic brand's price as if it were on sale, when it's always cheaper than other brands. If you're one to scan store shelves for sale prices, take an extra moment to make sure there's an actual markdown involved.

Extended warranties. It "virtually never pays" to pay extra for a warranty that picks up where the original one leaves off, said Lisa Lee Freeman, editor in chief of ShopSmart, published by Consumer Reports. Whether it's cars, computers or appliances, the instances are so rare when you'll get your money's worth that ShopSmart never recommends extended warranties. Either the products don't break down, Freeman said, or fixing them will cost less than the extended warranty.

Alluring store credit card offers. Some retailers are stepping up their push to persuade you to take out their store credit cards, often with offers of 10 percent off your purchase. When money's tight, this can seem like an especially attractive offer. But keep in mind that opening too many new credit card accounts can hurt your credit score. Besides, when you have too many card accounts, you're more likely to forget to pay one of them — and that, too, would damage your credit. Reject the offers unless you're definitely going to pay off your card each month and not incur the high interest rates, don't have a lot of credit cards already, or you're making a major purchase and you're going to cancel the card afterward.

Limited-time-only offers. It's increasingly popular for stores to limit how much and how long they offer certain types of merchandise for sale. It's true that some styles or designers might not be around in a few weeks. But try not to let that cloud your decision-making while shopping. Do you really need anything so badly that you must buy it right then, if even the sale price doesn't really fit your budget?

Two for $5/buy one, get one free. Just because a product is being pitched in big letters as a two-for deal doesn't usually mean you need to buy two. Check the small print to see if it notes that just one of the items costs $2.50 — or half of whatever promotional price is being offered for two. On the other hand, if there's a "buy one, get one free" deal, it doesn't always mean you need to get two. Sometimes, stores will just ring up one at half price, as grocer Harris Teeter will do, said Erin Gifford, of AOL's Shortcuts service, which links coupons to store loyalty cards. If the item isn't perishable or a severe test of your calorie-counting, Gifford suggests buying in bulk, "stacking" coupons from stores and manufacturers and using them at once to get an even deeper discount on a sale price.

Being a payment buyer. Car sales people will often ask you how much you can afford to spend a month. Don't ever start there. That figure merely helps the dealership disguise the true cost of the car, said Phil Reed, consumer advice editor at the automotive Web site Edmunds. He suggests arranging your financing before you go to the dealership and making clear you're a cash buyer. Then, because dealers almost always offer the best financing rates, discuss whether they can do better than your deal when it's time to sign on the dotted line. Negotiate the best deal on the purchase price of the vehicle by checking www.Edmunds.com, which will tell you what other buyers are paying for the same new vehicle in your area and what incentives might be available.

Skipping the research. Sure, that nice salesman at the electronics store or car dealership can tell you everything he wants you to know about what he sells. But do you really want to rely solely on that? Online consumer reviews and price-comparison tools have made doing your homework on purchases easier than ever. If you want to browse, do it at your computer. Don't leave home without doing research on big purchases — unless you're certain you can walk away from that sales professional without making a purchase.

No payments, no interest for six months. If you can't afford that couch or computer right now, there's a good chance you won't be able to afford it in six months, either. Resist the temptation to slide for a half year if there's any chance you'll either forget or be unable to pay at the end of the period. If you don't pay the full amount after the stated number of months, you'll have to pay all the back interest that accrued on top of new interest charges. It can also wreak havoc on your credit score.

Today-only deals. If a store or salesperson insists that a certain price is good only for that day, walk away unless you're certain it's the exact product you want at a price you can afford. With cars, it's usually just a come-on, except in rare cases, such as when it's done because an incentive from an auto manufacturer expires near the end of the month, Reed said. Car salesmen will often ask, "What do I have to do to get you into this car today?" said Reed, who sold cars undercover in 2001 as research for a series of articles. They're just trying to excite you, he said. During his training as a salesman, Reed said, he was shown an "emotion meter," detailing the range of most people's emotions and how to turn them up.