A way that I teach my students this concept is by first teaching them all 12 notes in music. They are as follows;

A - A#/Bb - B - C - C#/Db - D - D#/Eb - E - F - F#/Gb - G - G#/Ab

These are all the notes that we know in western music, and what all music that we know is based on. This does not deviate from instrument to instrument. What is nice about the guitar, like the piano, is that we can take a very visual approach to learning this concept. When you move from note to note (left to right, right to left), you are moving in half steps. This is equal to moving up or down one fret on the guitar. Let's apply this to the High E string;

Here are the 12 frets and their corresponding frets;

0 (open string) - E
1 - F
2 - F#/Gb
3 - G
4 - G#/Ab
5 - A
6 - A#/Bb
7 - B
8 - C
9 - C#/Db
10 - D
11 - D#/Eb
12 - E

Notice that you started and ended on the same notes. The two dots on the 12th fret of your guitar are what really guide you to knowing that you naming the notes correctly. Try this method on all 6 strings, as you will begin to memorize the notes as they apply to music and relate that to guitar.

Try doing this for the A string; simply quote this part of the forum and copy it and fill in the notes to show that you have this concept under your fingers. Simply fill in the corresponding frets with the correct notes.

Notes on the A String:
0 (open string) - A
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -

[U]Give it a shot![/U]