You can't predict investment returns, but you can predict how much you'll lose to high fees. That's why you should stick to funds with low annual expenses. There are no guarantees, of course, but funds with lower costs tend to outperform peers that operate with the drag of higher fees.
Look up how much the funds you own (or want to buy) charge by punching in the fund ticker in the Get-Quotes box above. As a general guideline, you shouldn't be paying more than 1% a year for a U.S. diversified stock fund or 0.80% for a bond fund.
You can easily reap this low-fee advantage by investing in index funds. Most charge less than half of the 1% to 1.5% that's common for regular mutual funds, and some charge as little as 0.07% a year - just $7 a year for a $10,000 investment.