Tuning a guitar is a very simple process once you learn how to do it. Lets take a look at your guitar. The strings on your guitar go from top to bottom.
E – The lowest in pitch and thickest string (aka the low E string)
A – 2nd thickest string
D – 3rd thickest string
G – 3rd thinnest string
B – 2nd thinnest string
E – The highest pitched and thinnest string (aka the high E string)
Tuning a Guitar – Guitar Tuner
This is whats known as standard tuning. There are other variations of tuning ( tuning a guitar variations ) but in this demonstration we’ll just be concentrating on standard tuning since it is the most widely used. When tuning a guitar you’ll usually want to start with the low E string (thickest string). You’re going to need a reference note for the low E. Above ive supplied a simple tuner to help you hear the pitch for each string. You could also use a piano, another guitar, a pitch pipe or a chromatic tuner. If you happen to have none of these available then you can leave the Low E string as is and tune the rest of the guitar to the Low E string. The most important thing is that the guitar is in tune with itself. Now lets get started.
Tuning a Guitar – Walkthrough
Assuming you have the low E string in tune.
1- Put your first finger on your left hand on the 5th fret of the low E string.
2- Now strum just the low E string with your finger on the 5th fret. You are now playing an A. This is the same exact note that the next string should be when played open.
3 – As you play the 5th fret on the low E string alternate between that and playing the A string open.
4 – Now adjust the A strings tuning peg in order to match the tone of the 5th fretted low E string.
5 – Repeat the process for the D and the G strings. To tune the D string you put your finger on the 5th fret of the A string and play the D string open. For the G string you put your finger on the 5th fret of the D string and play the G string open. Are you seeing the pattern here 
6- Heres where it gets tricky. In order to tune the B string you have to move your finger to the 4th fret of the G string (not the 5th fret this time). The G strings 4th fret is the same not as the B string played open.
7 – To tune the high E string we go back to the old pattern and place our finger on the 5th fret of the B string which will be the same not as the high E string played open.
8 – Congratulations you’ve just learned the secrets of tuning a guitar!
Guitar Tuner courtesy of the folks at Wimpy Player
