Buy comfy sneaks

You shouldn't buy kicks that hurt, bottom line! "Your shoes should feel comfortable from the first step," says Andrew Kastor. So shop in the evening—your feet swell during the day and stop in the late afternoon, so you want to shop when they're at their biggest. Also make sure the sneaks are a little roomy—enough so that you can wiggle your toes, but no more than that. They should be comfy from the get-go, but Kastor says they'll be even more so once you have a good 20 to 40 miles on 'em.