Whereas much of rock 'n' roll and pop guitar requires making chord shapes and strumming them in a rhythmic fashion, bluegrass guitar mainly uses these chords to make single-note arpeggios, breaking them up by playing individual strings. By playing these strings, one at a time in succession, it gives the illusion of extremely fast and difficult playing, even if your fingers are doing most of the work instead of your left hand.
Decide what style of bluegrass guitar you want to play. Popular methods include Carter style, which is a blend of conventional rhythm and lead guitar playing, and cross-picking, which is an approach highly influenced by banjo roll technique. In addition, some players prefer flat picks while others prefer finger picks. Regardless of what you choose, you will always be playing a melody with harmony notes, so find what appeals to you the most and stick with it.
Once you sit down to practice bluegrass guitar, learn the melody of the piece you want to play. This is the most basic part of the song, and should be the memorable, hummable line you hear above everything else. One song you might try to learn is “Black Mountain Rag,” which is a traditional tune. Once you can adequately play the melody, it is time to fill in the other harmony notes. Like any type of music, bluegrass guitar uses conventional guitar chords. The difference here is that you usually play these chords broken up, one string at a time. The rhythm you will be playing is constant eighth notes, spoken as “one-and-two-and-three-and-four-and.” Since the melody won’t be constant eighth notes itself, you add in strums of strings that are part of the chords to fill in the gaps. Usually, the harmony part is simpler than the melody, so as not to steal attention away from it. Some basic exercises for practicing the technique necessary for bluegrass guitar involve making a specific chord shape, like “G”, and practicing by playing each string individually in rhythmic eighth notes. Then try playing every other string in the same rhythm, finally skipping freely between each of the six strings, creating more interesting and melodic playing than conventional strumming. By combining this with the melodies you learn, you are on your way to playing guitar in the bluegrass tradition.