Watch the Alternate Note Placement online guitar lesson by Brad Carlton from Guitar Lab: Boogie-Woogie
As the title of this lesson implies, knowing the options of where to play something greatly increases your options for constructing variations on a line. This is critical when adding additional voices. We play an instrument which has multiple locations for the same note and when combined with fingering options, it can be quite overwhelming. But therein lies the great treasures of our instrument. One of the greatest "rut-busters" that I know of is this issue of alternate note placement.