In this video from The Motley Fool's "Ask a Fool" series, Fool analyst Matt Argersinger takes a question from a Fool reader who asks, "How can I understand the effect of maximum sales charges and expense ratios when determining which mutual fund is best? I tend to get seduced by the 1-, 3-, and 5-year total return percentages, and 'forget' that these funds also COST something to be in."