Extended warranties From DVD players to flat-panel TVs, practically all consumer electronics are backed with manufacturer warranties that last anywhere from 90 days to one year. However, many retailers want you to buy extended warranties for your purchases. They'll lure you with promises of free replacements and in-home repairs. But the truth is, you rarely need them, and you can't be sure that you'll be able to use it if the store goes bankrupt. Even if the store is stable, it's in part because extended warranties are a huge profit center. However, if you do sign up for the extended warranty, remember to check when coverage begins and what it doesn't cover. Sometimes what it doesn't cover is more important than what it does. Credit card debt As tempting as it may be, putting all of your holiday purchases on your credit card (when you can't immediately pay it off) is the biggest shopping mistake you can commit. In addition to charging you interest, credit cards can quickly become financial burdens that make the holidays into a year-long annoyance. We usually suggest that you always pay via credit card because of the extra consumer protection it provides over other methods of payment. (For example, you're almost entirely protected from credit card fraud so long as you report it.) However, rather than rack up debt, it may actually be better to pay with cash or a debit card, or to use a layaway plan. (Find out which stores offer the best layaway plans here.) If you can't afford to make your purchases with cash, chances are you shouldn't buy those items in the first place. However, if you must pay with credit, use the card with the lowest interest rate so you can quickly pay off your debt the following months. High shipping costs With Christmas a week away, it's easy to fall into a frantic shopping frenzy as you race to complete all of your purchases. But before you pay any absurd overnight shipping fees, take a look at our shipping deadlines to find out what cut off dates you need to be aware of. Also, if you plan accordingly, you might be able to find some excellent last-minute shipping deals on a lot of your online purchase. Louis Ramirez is dealnews' Features editor.