If you play the guitar, you know the strings cut in your fingers as you press them against the frets to sound different notes up and down the fretboard. Building up your fingertips is part of the sore, but necessary, daily leavening process of learning how to play the guitar. The idea, however, is not to build callouses on your fingertips. The goal is to build up the inside of your fingertips while leaving the outer skin smooth. If your fingertips look like mine below after a gruesome practice session — find a nail file and take off that thick, deadening, skin!