The easiest and most accurate way to tune your guitar is by using an electronic tuner. An electronic tuner allows you to tune each string individually to the tuner, by indicating whether the notes are sharp (too high) or flat (too low). There are basically two types of electronic tuners.
One type uses the position of a needle to indicate the correct pitch of a note and the other type uses a row of lights to indicate the correct pitch of a note. Most electronic tuners are relatively inexpensive and simple to operate.