Investors can avoid common fees from online brokerages

— -- Even with discount brokerages, cost-conscious investors have to beware.

An aggressive price war between brokers has driven down the costs of trading commissions dramatically the last two years, and it now typically costs $10 or much less per trade at most discount brokerages. Yet, despite the falling commissions, investors' satisfaction over the charges and fees they're being hit with fell in 2011, an analysis by J.D. Power & Associates found.

Most of the disgruntlement isn't about commissions, which are boldly advertised, but rather a bevy of hidden costs. Just 36% of investors say they completely understand all the fees they're being charged by their brokers, J.D. Power says. And a little fee here and a one-time cost there quickly add up.

By paying attention, though, smart investors can avoid nearly all these hidden fees and other charges and keep more money in their pockets. Here's a guide to assessing what fees you should absolutely not be paying, or how to avoid them:

Exchange traded fund costs

ETFs have revolutionized trading by allowing investors to buy entire baskets of stocks or other assets with the ease of buying a share of stock. Many ETFs have annual expenses that are well below comparable mutual funds.

But since you pay the standard stock commission when buying ETFs, fees can rack up fast. An even less apparent fee to watch for is the "spread" — the difference between the price you must pay for the ETF and the price you'd get at the same moment selling. For instance, if you pay $10 for an ETF that you could only get $9.80 for if you sold at the same time, you're essentially paying a 20-cent commission.

How to avoid them: If you're paying a commission to buy or sell ETFs, stop right now. Nearly all the major brokerages, including TD Ameritrade, Charles Schwab and Scottrade, charge no commissions on many ETFs that cover the key asset classes. To avoid the cost of the spread, consult money.usatoday.com, enter the ETF symbol and look at the difference between the "bid" and the "ask" price. Stick to ETFs where the difference is only a few cents. The more popular an ETF is, the smaller the spread, which lowers the cost to you.

Transfer fees

Want to switch to another brokerage, perhaps to take advantage of commissions that better suit your investment style? Get ready to get hit with a cost many investors find to be the most outrageous: a transfer fee, or ACAT. Most brokerages charge $50 or more if you decide to move your money out.

How to avoid them: ACAT fees can be completely avoided if your portfolio is filled with money-losing investments. Rather than transferring your account, just sell your positions and take the capital loss. You can then withdraw your cash and pay no fee.

For most investors, this is either not an option or might be too severe or incur tax ramifications. In these cases, be persistent with the brokerage you're moving to. Some, like TD Ameritrade and TradeKing, advertise they'll reimburse your ACAT fees if you move your account to them and fulfill requirements, such as staying for a set period of time. But always ask. Many brokerage firms will reimburse the fees for new customers.

Paper fees