Watch the A Dorian Mode online guitar lesson by Brad Carlton from Guitar Lab: Dorian Dominance
This lesson presents the seven traditional position forms of the A Dorian mode. My system of organizing these forms is based upon the lowest available note on the sixth string. Whatever scale degree this starting note is will be the title of the scale form. Traditional scale forms reside within a four fret span with each finger assigned to its respective fret. This also allows for a first finger extension and a fourth finger extension enabling you to cover a six fret span. The lowest available scale form in the A Dorian mode would be scale form V because the lowest available note on the guitar is a sixth string open which is an E. E is the 5 in A Dorian. This process is repeated with each of the remaining six scale degrees.
As you study the A Dorian mode, you will notice patterns emerging with regard to adjacent notes in the scale. Be sure to memorize the intervallic pattern of this scale. All you need to remember is that the half steps occur between the 2 and b3 and also between the 6 and b7. All the other scale degrees are a whole step apart. This means that if you're viewing groups of three adjacent scale tones, they will fall into the following patterns: whole step half step (1 2 b3 and 5 6 b7), half step whole step (2 b3 4 and 6 b7 1), and whole step whole step (b3 4 5, 4 5 6, b7 1 2).