Using a tuner to tune a guitar is much easier than relying on your ear and trying to match pitch with another instrument. A chromatic tuner is a type of electronic tuner that registers all notes of the musical scale, including sharps and flats, as opposed to some tuners that only register whole notes. You can tune your guitar quickly, easily and accurately with a chromatic tuner.
Prepare for tuning. Turn the tuner on. If your tuner has an input jack, you can connect your guitar to it via a guitar cable. Some tuners clip on to the headstock of the guitar. Other tuners simply need to be set on a flat surface near the guitar.
Pluck the high E string, which is the thinnest string and the one closest to ground when you play the guitar.
Watch the tuner to see what pitch registers. The available pitches on a chromatic tuner are A, A#/Bb, B, C, C#/Db, D, D#/Eb, E, F, F#/Gb, G, G#/Ab. The pitch that you are aiming for is E. If your pitch is too low (flat), tighten the tuning key. If the pitch is too high (sharp), loosen the tuning key. When the pitch is absolutely accurate, your tuner should read "E" and indicate no sharpness or flatness in the E pitch. Some tuners show this precise accuracy by a needle that points to a center mark or by a light or electronic display.
Repeat steps two and three for the other five strings. They are (in order from high to low): B, G, D, A and low E.
Expect to retune new guitar strings often for the first few hours of play, since they will stretch a great deal.