Watch the Modal online guitar lesson by Brad Carlton from Guitar Lab: Super Sustain
The progression we will be dealing with is a I V vi IV in the key of C. That means the chords will be C, G, Am, and G. The first chart you should look at is the master chart of the C major scale over the entire fingerboard. This is our source for every note we're going to play.
In this lesson we will be applying a modal approach over this progression. Locate the chart titled: Mode Analysis Master Chart. This chart reveals how each note in the C major scale functions against each of the four chords. This is also revealed in diagrams 1a through 1d. A quick overview of modes is as follows: C Ionian is the C major scale played from C to C, G mixolydian is the C major scale played from G to G, A Aeolian is the C major scale played from A to A, and F lydian is the C major scale played from F to F. The scale degree numbers that appear in the above mentioned charts reflect how the note functions in reference to the prevailing chord. These numbers would be arrived at by comparison of the note to the major scale of the prevailing chord. Your ultimate goal is to be able to see all the information presented in diagrams 1a through 1d on the fingerboard. This obviously isn't going to happen overnight so be patient but persevere in this quest for knowledge.