
Before we begin, let's clarify exactly what a "chromatic scale" is. In Western music, there are 12 different musical pitches (A, Bb, B, C, Db, D, Eb, E, F, Gb, G, Ab). The chromatic scale includes EACH of these 12 pitches. So, we could actually play a chromatic scale simply by sliding our finger up one string, playing each fret.
chromatic scale pattern guitar lesson two octave picking practice warm up exercise Our reason for learning the chromatic scale, at this point, is simply as a means of improving our finger technique. Start by placing your first finger on the fifth fret of the sixth string, and play that note with a downstroke. Follow that by using your second finger to play the sixth fret of the sixth string (with an upstroke). Then, your third finger should play the seventh fret on the sixth string, and lastly, your fourth (pinky) finger should play the eighth fret.
Now, move on to the fifth string. Playing this string will require a "position shift" in your fretting hand. Move your hand position down one fret, starting on the fourth fret of the fifth string with your first finger. Play each note on that string, as you did on the sixth. Repeat this process on each of the sixth strings (notice that you DON'T switch positions on the second string. This is because the second string is tuned differently than the other five.)
When you reach the first string, play the first fret with your first finger, as usual. Then, immediately switch positions, and also play the second fret with your first finger. This step allows you to reach the fifth fret, thus completing the two octave A chromatic scale. When you've reached the end of the scale, try playing it backwards.
Source : guitar.about.com