Also, for good nail health, NEVER destroy the cuticle. Push it back gently as the nail grows out. One of the biggest problems with my hooked/flat nail is that the cuticle naturally (on its own) separates from the nail. I believe this is the main cause for the nail to grow flat (which in my case is the cause for it to curve).
One Ring to rule them all, One Ring to find them, One Ring to bring them all, and in the darkness bind them.