It is best to file your nails only when the white part of the nail-the tip-has grown ¼ inch from the nail's stress point, which is where the free edge meets the pink part of the nail plate. If you file your nails before this point, it can weaken them. At the same time, if you let your free edge grow longer than the nail plate, it is certain your nail will break.

Do not file from side to side, which can weaken the stress points of the nail's free edge. Be sure to go from corner to center in one direction, using the groove on the side of your nail as a guide.