The open strings of a guitar from the thickest to thinnest are as follows:
E – the thickest or lowest sounding string is known as the 6th string
A – is the 5th
D – is the 4th
G – is the 3rd
B – is the 2nd
E – the thinnest or highest is the 1st string
Now that you know the names of the open string you will need to know how to match to the note. If you see a natural note with a little sign that looks like a lower case “b” next to it that little sign is a flat sign. In the context of tuning, when we say a note is flat, that means that the note too low and needs to come up. A sharp sign looks like a tic-tac-toe sign. As far as tuning goes, when we talk about a note being sharp, that means that the note is a little bit too high and it needs to come down.
There are a few different methods of guitar tuning.
An electronic tuner has a couple of ways of telling you if a note is sharp or flat. Those two ways, generally, are lights or needles. If the lights on your electronic tuner are off to the left, that means your note is a little flat and it needs to come up. If they are off to the right that’s telling you that your note is little bit sharp and it needs to come down. You could also have a needle that basically does the same thing. If the needle is off to the left your note is a little bit flat. If it’s off to the right, the note is a bit sharp and it needs to come down.
This method uses your computer's microphone to hear the note your string is sounding and will show you if you are sharp or flat of the correct note.
The first method will play a recording of the string being played. You will then match your string to that audio.
Standard Guitar Tuning Method:
Step 1: The E String
Tune the bottom E, as accurately as you can. Chances are it’s close to being in tune if you have previously tuned the guitar as it is the thickest string so it’s the least likely to have detuned itself. You can
Step 2: The A String
Place the first finger of your left hand just behind the fifth fret on the bottom E string. That’s an A note. Keep your finger on that fret. Now pick the fifth and six strings in turn, gently adjusting the fifth string tuning peg until the two notes are the same.
How to tune the A String on a guitar
Step 3: The D String
Place the first finger of your left hand just behind the fifth fret on the A string. That’s a D note. Tune the 4th string (the D note) to that.
Tuning the D String
Step 4: The G String
Place the first finger of your left hand just behind the fifth fret on the D string. That’s a G note. Tune your G string to that note.
Tune The G
Step 5: The B String
Place the first finger of your left hand just behind the fourth fret (note the B string is the only one that comes from a different position the forth fret, the rest are from the 5th fret).
Tuning the B String, from the 4th fret of the G
Step 6: Tuning the E String
Place the first finger of your left hand just behind the fifth fret on the B string. That’s a E note.
Check out this great video about how to tune a guitar.