Most credit cards make borrowing money expensive. On fee-based credit cards, the average rate is 23.37%, according to Federal Reserve data. For every $1,000 of debt, you pay about $233 per year in interest.

In comparison, 0% APR credit cards seem like an incredible deal. These have a 0% APR for an introductory period. During this period, you are not charged any interest.

You can save quite a bit of money with this type of card, if you use it correctly. But there are a few common mistakes that could cost you thousands of dollars.

1. Not getting the right type of 0% APR offer

There are two types of 0% APR intro offers:

• Purchases : You don’t pay interest on new purchases. This type of offer is used to reimburse major expenses over time.
• Balance transfers: You don’t pay interest on balances you transfer from other cards. This type of offer is used to refinance credit card debt, which means moving it from a card with a high APR to a balance transfer card with a 0% introductory APR.

Some cards offer both for equal periods. Other cards only offer one of the two, or one for much longer than the other.

For example, a card may have a 0% introductory APR for 18 months on balance transfers, but only for six months on purchases. You wouldn’t want to get this card if your goal is to pay off your new purchases over time. Or, a card may have a 0% introductory APR for 12 months on purchases, but balance transfers are charged the regular APR from the start. This wouldn’t work if your goal is to refinance your credit card debt.

If you’re looking for a way to save on your credit card debt, a long-term balance transfer offer is exactly what you need. Click here to see our curated list of top balance transfer cardswith an introductory APR of 0% for up to 21 months.

2. Using 0% APR as an excuse to spend too much

One of the risks of 0% APR cards is that they can convince you to spend money that you otherwise wouldn’t. You know you don’t need a new tablet, and you didn’t even open a 0% APR card for it. But you really want it, and it’s not like you’ll be charged interest (yet).

You continue to go into debt, even if the APR is 0% at the moment. And you will still have to repay all the money you borrow. If you spend $3,000 more because your card has a 0% intro APR, that’s $3,000 to pay off in the future. It will also start costing you interest once your card’s introductory period is over.

Plan what you will finance with your 0% APR card before opening it. Perhaps you want to use this type of card to pay off a costly auto repair over time without paying interest. This is a good way to use an introductory 0% APR. But resist the temptation to make extra purchases you don’t need.

3. Make only minimum payments

Another danger with 0% APR cards is that they remove the pressure to pay off your balance. There are no immediate consequences if you only pay the minimum each month. For this reason, some people stop putting much effort into paying off their credit cards.

But the 0% introductory APR will eventually end. When this happens, the APR will increase significantly – perhaps as much as more than 20%, if your card’s interest rate is similar to the national average. If you’re still thousands of dollars in debt when this happens, you’ll start paying high interest charges.

Come up with a payment plan that will pay off your card balance during the introductory period. Let’s say your card has an introductory APR of 0% for 15 months. You use it to pay $4,000 in medical bills. You’ll need to pay around $267 per month to have that balance paid off during the introductory period. This assumes you no longer spend with the credit card.

A 0% APR card is a valuable money-saving tool. You can use one to finance purchases or get a balance transfer card to help pay off credit card debt. Like any other tool, it is important to know how to use it. Now that you know what to avoid, you can find the best 0% APR credit card for your needs and make sure you get the most out of it.