You may be a savvy enough banker to know that you should be careful when using ATMs -- especially if you're doing so at night, at an exposed machine. But our friends at recently pointed out some other things to be watchful of when using ATMs.

For example, if you use an ATM that belongs to a bank at which you don't have an account, you'll be socked with fees. You'll likely be slapped with a fee by the other bank for using its ATM. And you might also be charged a fee by your own bank for using another bank's ATM. You might think this isn't a big deal, but we're not talking 35 cents here. The average total fee for such a transaction is $2.91. If you paid this just once a week, you'd be forking over more than $150 per year. What, that still doesn't seem like a big deal? It should. If those $150 were invested and grew at 10% per year, they'd become more than $1,600 in 25 years. If you use the other bank's ATM twice a week, you'll likely fork over more than $300, and could lose more than $3,200 in 25 years.

Things get worse, though. Bankrate notes that in 2005, Americans will hand over more than $4.3 billion in ATM withdrawal fees when we use another bank's ATM. Yikes. Is the trend at least dropping in value over time? Nope. A CBS News report noted: "... Small, almost omnipresent charges add up. The average surcharge for a non-customer at a bank's ATM is $1.54. And, on top of that, the customer's own bank charges an average of $1.37. Both of these figures represent a new high for ATM fees, according to Bankrate."

If this sounds to you like something fishy is going on, you're not alone. Last year, a class action suit was launched against banking enterprises such as First Data (NYSE:FDC), JPMorganChase (NYSE:JPM), Citibank (NYSE:C), SunTrust Banks (NYSE:STI), Wachovia (NYSE:WB), and Wells Fargo (NYSE:WFC), suggesting that the firms worked together to charge inflated ATM fees.

Meanwhile, though, you don't have to be fleeced. You might, for example, simply use only your own bank's ATMs. If it's a small bank, check to see if it's a member of a wider ATM network. You might also look for another bank, one more suited to your needs. Some banks have such a widespread local presence that using "foreign" ATMs isn't an issue. Other banks will reimburse you for fees charged when you use another bank's ATM.

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First Data is a Motley Fool Inside Value pick; JPMorgan Chase is an Income Investor selection.

Longtime Fool contributor Selena Maranjian does not own shares of any companies mentioned in this article.