Many hairstylists offer free bang trims. But if yours doesn't (or if you just don't have time for monthly visits), you can take matters into your own hands.
All you need is a pair of sharp scissors (try Tweezerman Stainless 2000 51/2 trimming shears, $25), a mirror, and a few minutes, with no distractions.
Only cut bangs dry—"Hair is longer when it's wet, so you run the risk of going too short," says hairstylist Patrick Melville, of the Patrick Melville Salon in New York City—and hold them taut between your index and middle fingers as you trim in small sections, from one temple to the other. Go slowly, in little increments, because "if you take off too much in that first snip," says Patrick, "you're doomed" (or at least sentenced to an awkward grow-out period). Don't go shorter than the bridge of your nose—once you release the bangs, they'll jump up as much as half an inch.