The finger nails of the right hand play an important role in shaping the sound you will get from the instrument. I'll explain how to shape and use the finger nails of the Right hand so that you can get any sound which your instrument is capable of producing.
Before starting this lesson, make sure you have a good fingernail clipper and a set of sand paper or emery boards with a least 3 different grit surfaces. The finest grit should actually feel smooth to your touch. The middle grit should have enough roughness so that if you file your fingernail it should produce a fine white powder but should not remove too much of the nail. The heaviest grit should be coarse enough to file the nail so that it can be shortened and shaped. Notice that I didn't specify any absolute grades. That will depend on the hardness of your nails. A grit that will easily cut through soft nails may not be nearly coarse enough for thicker, harder nails. The next section in this lesson will get into a little more detail.
Care and Shaping of the Finger Nails
You can always tell that a person is either a classical guitarist, or, has a bad fingernail biting habit on just one hand with a meticulous fetish for beautifully shaped nails on the other. I actually got my first job in Engineering when I was asked by the Engineering Manager who interviewed me to let him see my hands. When he noticed that my right hand fingernails were perfectly manicured and my left hand nails were very closely trimmed, he smiled, spent 45 minutes of the next hour discussing classical guitar and, hired me for the programming position.
Your fingernails play a very important role in producing a good sound on the instrument. It's pretty easy to care for the nails on your left hand - you simply trim them as close as possible with a nail clipper without drawing blood. The right hand requires a lot more attention. There are three attributes of the right hand fingernails that need attention: length, shape, and edge. Your ideal fingernail shape and length can only be achieved after much experimentation. The edge required for a good sound is more absolutely determinable - it must be smooth.
Shaping your fingernails
When your nails are ready to use for playing, the entire edge of the finger nail should be smoothly rounded with no breaks or rough spots. If you look closely at the edge of your fingernail with your fingers pointing straight into your eyes, they should be as smooth as the edge of a fine crystal wine glass. If you slide the edge of the fingernail of your right thumb over the edge of each of the other three playing fingers of the right hand, you should not be able to detect any roughness or breaks in the surface. An edge like that is absolutely necessary so that no extraneous noise is created by your fingernails as they slide over the strings while you're playing.
To create the required edge, you first shape and adjust the length of the fingernail by using the coarsest grit emery board. I have seen great Classical Guitarists with fingernails that look like claws and others who have no fingernails whatsoever. My own experience has resulted in me having a fingernail length which causes the edge of the nail to extend about 1/8 inch above the tip of each finger when viewed from the palm of the hand with my fingers pointing straight up and held at about eye level. That length should be a good starting length for you but it is likely that you will decide to adjust it as you learn how the length of the fingernail affects the sound you want to produce.
The edge of the nail should follow the shape of your finger tip and there should be no discontinuity at either side of the fingernail. In other words, the curve of the fingernail should extend smoothly to the point where your fingernail touches the cuticle. Once the nail is coarsely shaped you remove any jagged edges or cracks by using the middle grit. This step also gives the nail it's final shape. Once you are satisfied with the shape and length, you polish the edge with the finest grit emery board.
Concert Classical Guitarists usually carry a fine emery paper with them when they perform so that they can smooth out any rough spots on their fingernails which might be caused by contact with the three metal wound strings of the guitar during a performance. You might at first think this fastidious attention to the fingernails is a little strange, but you will quickly learn to feel and hear the difference it makes when you play.