Watch the Simple Intervals online guitar lesson by Brad Carlton from Guitar Lab: Dorian Dominance
This lesson examines the A Dorian mode in intervals of fourths. Diagram 73 shows the layout for these on the fourth and third strings. This same map will apply to all other string groups except the third and second strings. Diagram 74 shows the layout for the third and second strings.
As you play these intervals, try to see the two linear Dorian mode scales that exist on each string.