Be wary of any mutual fund charging a management fee higher than 1 percent (a few stellar managers may be worth it; most are not). A manager with a high buying and selling rate (called "turnover") should also set off warning bells. If you aren't interested in watching your fund manager like a hawk, stick with an index fund, like one from Vanguard, where expenses are typically around 0.2 percent. And if you're trading stocks, don't be fooled by low commissions: They add up.