• 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 thinest or highest is the 1st

The most common method for tuning both Electric and Acoustic guitars – and the one you can use when no other instrument or Guitar Tuner is at hand is:

Standard Method

Step 1: The E String

Tune the bottom E, as accurately as you can. Chances are it’s in tune anyways, being the thickest string it’s the least likely to detune itself than any of the others. If you have another instrument such as a Piano (which stays in tune for years), you can tune it to the 1st E below middle C. If you have no device or instrument handy just try to get it as accurate as possible, what really counts when you are playing is that the guitar is in tune with itself and any other instruments you might be playing with.

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.

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.

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.

Step 5: The B String

Place the first finger of your left hand just behind the forth 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).

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.