If your nails need a trim, use two snips from a small pair of scissors to cut them straight across. (Stronger toenails are often hard to cut, so trim them after showering or soaking them in water.) Then use a file to hone them into a square shape with rounded edges. This shape won't catch or tear as easily as oval nails, says Elisa Ferri, a manicurist in New York City. Always file nails in one direction, instead of sawing back and forth, which can cause splits.