Pick up your guitar and hold it in standard position. If possible, tune the 6th string, the low E, to a piano, an electronic tuner, or other device. Consult an online tuner to accurately determine the low E note. If this is not possible, estimate the low E string's correct note; this will be the note you will tune from. Keep in mind that tuning your guitar with octaves without the low E note in concert pitch will tune your guitar to itself, but not necessarily to other instruments.
Locate the low E string. Play it open without fretting and listen to the tone. Move down one string to the A string. Locate the 7th fret on the 5th A string, hold the string down on that fret, and play the 5th string. The low E string and the A string at the 7th fret should be the same tone in different octaves; the E string will be exactly 12 half-steps below the 5th string 7th fret, otherwise known as the lower octave. Play both notes several times and listen to hear if they are the same tone. If they are not the same, adjust the tuning peg associated with the A string until the notes ring true.
Play the A string open after it is in tune with the E string. Move down the neck of the guitar to the 4th string, also called the D string. Play the 7th fret on the D string and compare it to the open A string tone. The notes will share a tone, although they will be in different octaves. Adjust the D string tuning peg until the open A string and the D string at the 7th fret are the same tones.
Play the open D string. Travel down a string to the G string, also called the 3rd string. Play the 7th fret on the G string while playing the D string open. Turn the G turning knob until the notes match.
Sound the open G string. Move down a string to the 5th B string, but this time play the 8th fret on the B string and compare to the open G string; this difference is due to the way the B string is tuned in relation to the other strings. Adjust the 5th string tuning peg to tune in relation to the G string.
Play the 7th fret on the E string and compare to the open B string. The notes should be the same, although in different octaves; turn the E string peg until the notes ring together. The guitar should be entirely tuned.