If you walk into a bank or credit union today to open a checking account with a debit card attached to it, you'll be faced with a new choice: if you try to make a purchase with your debit card and there's not enough money in your account, do you want your financial institution to authorize the purchase (and charge you a hefty fee for doing so), or would you rather the purchase be declined?

I may be making it sound like a no-brainer, but it may not be such an easy decision. When Credit.com polled consumers on this issue in May, we found that slightly more than half would choose to opt-in and avoid the embarrassment or inconvenience of having purchases declined.

Debit card overdrafts can come with a serious price tag. Fees for these overdrafts usually run $35 to $40 – even if you just overdrafted by a few bucks – and if you overdraft more than once, you may be hit with multiple fees.

The new rules that go into effect today, July 1, 2010, for new accounts, and August 15th for existing accounts. If you don't opt in (or don't even read the notice from your financial institution) you may find yourself being turned down for debit card purchases if your balance is too low. But that doesn't mean you have to opt in to this pricey protection. Here are a few alternatives:

1. Carry a back-up payment method, whether it's a credit card that you pay in full each month, or another debit card.

2. Find out whether your financial institution offers a less expensive alternative, such as tying your savings account to your checking account as a back up. There may still be fees for these transfers, but they are likely to be cheaper than standard overdraft protection.

3. Inquire about an overdraft line of credit. Again, this won't be free, but it may be cheaper.

4. Sign up for text message alerts if your balance falls below a certain threshold you set.

5. Avoid holds. If you use your card to get gas at the pump, there may be a hold placed on funds in your account that can freeze up a portion of your balance. Go inside instead, tell the clerk how much you'd like to put into your tank, and then pay for that amount at the register to avoid a hold.

What's your choice – opt in or opt out? We'd like to hear about it.

Gerri Detweiler – Personal finance author and Credit Advisor for Credit.com, Gerri contributes budgeting, debt recovery and savings information online. She is also the co-author of Debt Collection Answers: How to Use Debt Collection Laws to Protect Your Rights.