How to Tune a Guitar to Open G. Open tunings on a guitar are tunings which allow you to play a chord without holding down any strings at any fret, thus giving you an open chord. Open G tuning is the most common open tuning, used mostly for blues, slide guitar and some folk. Artists who use open G guitar tuning include John Fahey, Jack White of the White Stripes, Jimmy Page, and Joni Mitchell.
Tune your guitar to standard tuning (EADGBE).
Re-tune the low E string down a whole step to a D. To do this, loosen the string and compare it against the D string until it is the same note. The low string will be an octave lower than the D string.
Drop the pitch of the high E string down a whole step to a D also. Do this the same way as the low E string, by lowering the pitch until it matches the D string. This time, though, the high string will be an octave higher than the D string. Now you have DADGBD.
Change the pitch of the A string down to a G. Use the G string as a reference to tune the A string down. The string will be an octave lower than the G string. Now you have DGDGBD
You can use a standard guitar tuner or a chromatic tuner to make sure your strings are in tune. A piano is also a great way to check your pitches.
Using alternate tunings can make your guitar really out of tune. Make sure to check that all strings are in tune, not just the ones you changed. Using different tunings that your guitar and strings are not used to can affect all the strings' tensions. Chords are different in open G tuning. Trying to play the same chord fingerings as standard tuning will not make a pleasant sound.