When you are choosing crampons, bring your boots to the store to be sure they fit the crampons. With strap-on crampons, make sure the boot fits the frame. When you pick the boot up, the crampon should be snug enough to stay on without using straps. For step-in crampons, make sure the toe bail fits the shape of the toe welt on your boot, and that the heel lever snaps up tight. If you can just barely shove the heel lever into place, you have a great fit. On any crampon, the front points should protrude from the boots about a half-inch to an inch.
You’ll want to keep your front points razor sharp. Likely, you’ll need to sharpen them after every outing. A steel file (about $5 at any hardware store) will strop those dull points into shape; wear gloves to protect your hands in case the file skips and you rake your knuckles along the points. When you file, follow the manufacturer’s bevel, as it will already be at the optimal angle for the point.
With repeated sharpenings you may notice that the back, smaller teeth are now lower than the main point. When this happens the back teeth will lever the front point off its purchase. Bad! File the back teeth down until they can’t interfere with the front point, and sharpen them, too, while you are at it.
Some climbers like to give their front points a fishhook shape for toeing into rock holds. To get this shape, take a round (chainsaw) file and simply undercut the front point. Note that this will limit the number of times you can sharpen the front point—performance over longevity they say.