Check your mandolin frets and nut before you play. A fret is a wire that is incorporated into the fretboard perpendicular to the strings. Each evenly spaced set of fret wires creates a new note interval. The nut's purpose is to keep the spacing and the height of your mandolin strings even. Any problems with your frets or nut is going to change the sound of your plucking, perhaps creating buzzing or incorrect note pitches. These problems can also make your mandolin much harder to play.
You can use your fingers to pluck a mandolin, but the sound will not carry very far or cut through other instruments that are playing at the same time. Finger plucking may be ideal for classical or pop arrangements in which you do not want the mandolin sound to dominate ensemble playing. It can provide a smooth background for classical and pop melody lines.
Use a metal thumb pick when you want a bold, metallic sound---when carrying the melody is up to you and your mandolin. Sound created by a metal thumb pick can cut through the banjo in bluegrass, country and rockabilly music or through the pipes in Celtic music to shape or harmonize on the main melody.
A metal plectrum is most often a flat, three-sided piece of metal with rounded corners, less than an inch long. Any rounded corner can be used to pluck a mandolin string. The metal plectrum can bring out your sound in jazz pieces. in Celtic music, playing a mandolin with a plectrum ensures that your background notes won't cut through the piper's solo.
You can use the bottom point of a plastic or natural quill to pluck your mandolin strings. This sound mimics harpsichord notes heard in classical music. While the sound may not carry very far, it can give a distinct sound to each note in a plucked riff on a mandolin. It can also complement your unique playing style with an interesting visual.
The Portuguese guitarra is similar to a mandolin; therefore, a tremolo pick, used in guitarra music to give a "tremolo" or "trembling" quality to each note, can produce the same sound on a mandolin. A tremolo pick fits on the index finger; you pull outward to pluck a mandolin string.
Beginning mandolinists should start with finger plucking on pop or classical music pieces. Although finger plucking does not create the most dynamic sound, it does provide practice in controlling plucking movement and speed. Move on to a metal plectrum when you are comfortable with your finger plucking technique.