Before you begin playing, you must also know how the frets and strings are numbered (See Figure Below). The strings are numbered from the lightest (thinnest) to the heaviest (thickest). So the thinnest string is the 1st string and the thickest is the 6th string. A guitar in standard tuning is tuned to E-A-D-G-B-E. In other words, 6th string - Low E, 5th string -A , 4th -D, 3rd -G, 2nd -B, 1st -High E. Look at the diagram to find out how the frets are numbered. The 0 fret is also the open note on each string.
To tune your guitar, you only need to have one string tuned to any note, as long as you know which one it is. This is known as the reference point. Once you have this, tuning the rest of the strings is easy. There are various ways to find the reference point. You can use any of the following methods to tune one string or all your strings.
Piano/Keyboard: A keyboard is an excellent way to tune your guitar. Just tune the strings by matching them with their respective keys. The piano diagram covers one octave while the guitar diagram covers two octaves.