As we pointed out in Lesson 107, mutual funds aren't free. You should pay for professional money management if you need it, but paying enormous expenses to invest is like giving money away. That's because every penny that you give to fund management or to brokerage commissions is a penny you take away from your own return. Further, costs are one of the few constants in investing: They'll remain pretty stable year in and year out while the returns of stocks and bonds will fluctuate. You can't control the whims of the market, but you can control how much you pay for your mutual funds.
Unfortunately, fund costs are somewhat invisible, buried in shareholder reports and taken right off the top of your fund data. Morningstar provides a detailed breakdown of a fund's costs in the Expense section of all fund reports on Morningstar.com.