There's no way to totally prevent blisters, but you can stave them off, says Spencer Casey, senior manager at the New York Running Company in New York City. He suggests trading cotton socks for sweat-wicking ones made with Coolmax or Nike Dri-FIT. "Cotton traps moisture, which causes the friction that creates blisters," he says. He also suggests putting baby powder or BlisterShield (found at running specialty stores) on your feet pre-run.