Do you make the occasional math error? If you do with your debit card, you may pay $30 or more.

Even checking accounts—probably the most basic account in banking—contain a plethora of hidden traps these days and practice a type of “gotcha capitalism” that will get you if you don’t take a few steps to avoid the most common pitfalls.

Overdraft fees are the most common—and irritating—fees associated with checking accounts. The Consumer Federation of America’s survey of “courtesy” overdraft protection systems found that in 2005, banks charged an average of $28.57 to pay a transaction that overdrew a checking account. One bank in the survey charged $36.00 for its overdraft fee. And these fees have been on the rise since 2002.

The idea behind overdraft protection is that consumers benefit when the bank approves a transaction that overdraws the balance of an account and sends it into the negative. Covering the charge saves the consumer the embarrassment of a bounced check or a denied transaction. Many consumer groups liken them to a high-cost loan product: the bank essentially lends you the money to cover your transaction, and the fee serves as the interest. With fees this high, this “courtesy” comes at a high price.

Many banks that offer this bounce protection actually engage in practices that raise the likelihood and frequency of costly overdrafts. For example, when the bank receives multiple transactions on the same day, many banks will process a consumer’s largest transactions first. This maximizes the number of transactions that will occur in the red, which in turn maximizes the number of subsequent fees from smaller checks and transactions. Many banks also extend overdrafts at ATMs—when consumers are unlikely to be embarrassed by a bounced check or denied transaction. Many of these tricks are carefully documented in the upcoming movie “Overdrawn!”

Debit card users need to be on high alert. Some banks take this a step further and charge a fee for each transaction you make when the account is in the red—not just for the initial transaction that puts your account below $0. Let’s say you set out Saturday afternoon to run some errands, and you don’t realize you have only $25 in your bank account. You use your debit card to pay for $40 in groceries. That’s a $30 overdraft fee and puts your account at -$15. Then you buy a $10 lunch on the same debit card. There’s another $30 fee. What if you need to spend $40 filling up your gas tank? That’s a $30 fee. And God forbid you are thirsty and buy a soda for $1.50? That’s a $30 fee. In this scenario, the bank punishes you with $120 in fees because of your horrendous mistake.

Let’s say the next afternoon you check your bank account online and realize your error. You transfer money from your savings account to your checking account to bring it back in the black. The bank extended you a loan for the roughly 24 hours that you had no money in your checking account. The problem is, in this scenario, you borrowed $66.50 and paid $120 in fees.

Sound a little ridiculous? In banks’ own defense, many of them are known for reversing fees in these scenarios when customers complain. But a problem as big as this demands a bigger solution. The Consumer Overdraft Protection Fair Practices Act, introduced by Rep. Carolyn Maloney (D-NY), has a simple premise: it would require both new and existing accountholders to opt in to overdraft protection systems rather than being enrolled in them automatically. That is, customers should be able to choose if they want overdraft protection as it operates today or if they would rather not pay the fee and thus not give the bank permission to honor transactions that overdraw.

Rep. Maloney’s bill would also require banks to give their customers clearer information about the cost of overdraft protection. Customers could therefore better compare this service to its less-costly alternatives, such as linking their checking account to their savings account or to a line of credit.

Until better regulation is implemented, you can take a number of small steps that will reduce your frustration with your bank and let you keep your hard-earned money. One good idea is to never let your checking account dip below $100 if you can. This will save you from the check you wrote a month ago but forgot to write down, or when you swing by the ATM between errands without double-checking your balance.

Young people who work hard to pay their bills on time deserve financial services that help them build credit and assets to get ahead, not punish them for simple mistakes and leave them a step behind.