Tuning Guitar With An Electronic Tuner

An electronic or electric tuner is often a small, light weight, inexpensive device that listens to a plucked open string, compares it to an internal reference data base, then provides a visual indicator if the note is sharp or flat. As you loosen or tighten the string it gives you constant feedback until it is in tune.
These wonderful devices should definitely have a place in every guitar case because many people have greater visual than auditory acuity. They can be especially helpful if you have not yet developed an ear for sensing small differences between pitches.
The down side is that there is always a small but sometimes significant margin of error. Sometimes a string that may seem in tune according to the device may actually be out of tune relative to the other strings.
To offset this margin of error, slowly strum chords across the entire neck of the guitar and fine tune each string by what sounds good. Be careful not to strum only one or two chords at just one end of the neck. This will sometimes produce out of tune notes at the other end of the neck. Find a compromise tuning that best fits them all, (or at least the chords of the songs you intend to play).

Relative Tuning: Tuning A Guitar To Itself:

This means that one string is tuned using another string as a reference. Then that string is used as a reference for the next and so on. When all of the strings have been adjusted by this method they are said to be in tune relative to each other. It is worth noting that if the first string is out of absolute tune then all the other strings are now also out of wack. This means that they do not vibrate at the generally accepted frequencies or notes. A low E for example may not actually sound like a low E. The beauty of this method is that even though they are out of absolute tune they still can sound good when all are played together. This works fine if you are playing by yourself but if you are playing with other band members or even jamming with a CD, you will still be out of tune relative to them. Ideally you should tune the first string to an accurate reference note before moving on to the other strings.
We will discuss 2 methods: The Fret 5/4 and the Harmonic Fret 5/7 methods.

Steps for Tuning a Guitar by The Fret 5 Relative Method:

Step 1. Tune the low E (6th) string ( the thickest one ) to a known accurate reference note like an electronic tuner, an electric piano or an Online Guitar Tuner.
Step 2. Tune the open A (5th) string ( 2nd thickest ), by comparing it to the A note found at the fifth fret of the Low E (6th) string.
Step 3. Tune the open D (4th) string by comparing it to the D note found at the 5th fret of the A (5th) string.
Step 4. Tune the open G (3rd) string by comparing it to the G note found at the 5th fret of the D string.
Step 5. Tune the open B (2nd) string by comparing it to the B note found at the 4th fret of the G string. Note: This string is tuned to the 4th fret on the G string instead of the 5th fret. This is different than all of the other strings.
Step 6. Tune the open High E (1st) string ( thinnest ), by comparing it to the E note found at the 5th fret of the B (2nd) string.
Finally, slowly strum a few chords at different places up and down the neck to determine if you are satisfied with the tuning. If not, go back to step 2 and fine tune each string again.

Relative Tuning: Using Guitar Harmonics at the 5th and 7th Frets

This method is commonly thought to be superior to the Fret 5 method. However, Dan Erlewine, author of the book; How To Make Your Electric Guitar Play Great, published by Backbeat Books, strongly disagrees. He states that a guitar tuned this way will, quite simply, not play in tune. Dan goes on to give a complicated detailed explanation of why some of the harmonics used as reference notes are inaccurate.
Step 1. Learn How to Play Harmonic Notes Lay the fatty part of the tip of the first (index) finger on the low E string exactly above the 5th or 7th frets. Do not press down hard. Just let your finger rest on the string. Next, pick the string firmly with your strumming hand. Immediately after the string is picked lift off the finger resting above the fret. If your touch and timing are just right you will hear a beautiful, full, almost heavenly sound. If you are struggle to play the harmonic notes at the 5th fret go the 7th it should be a little easier. The 12th fret is actually the easiest even though you will not use it for tuning with this method.
Step 2. Tune the open high E (1st) string (thinnest) to a reference like an electric piano, an electronic tuner or an Online Guitar Tuner.
Step 3. Play the harmonic note at the 5th fret of the low E (6th) string and compare it to the open (non-fretted) high E (thinnest) string.
Step 4. Tune the harmonic note on the 7th fret of the A string to the harmonic note found at the 5th fret on the Low E string.
Step 5. Tune the harmonic note on the 7th fret of the D string to the harmonic note found at the 5th fret on the A string.
Step 6. Tune the harmonic note on the 7th fret of the G string to the harmonic note found at the 5th fret on the D string.
Step 7. Tune the harmonic note on the 7th fret of the High E (thinnest) string to the harmonic note found at the 5th fret on the B string.
This tuning method may not be ideal for beginners because it can be challenge to play harmonic notes. It can also be difficult to hear the difference between two harmonic notes.