The number 1 rule for long-term individual investors picking funds used to be simple: look for low fees, also known as low expense ratios. Investors do get rewards from low fees; but they should also watch out for higher, hidden fees in the same funds, as well as strategies that lure investors into higher-priced products or into paying more for advice. Instead of asking about low fees alone, ask what you are paying over 10 years, including all fees. "What is the cost, all in, for 10 years?" said Eric Johnson, Director of the Center for Decision Sciences.