Watch the Chord Root Targets online guitar lesson by Brad Carlton from Guitar Lab: Vertical Soloing
This lesson deals with targeting the root of each of the four different chords that comprise the IV V vi IV ii V vi progression that we are presented with. These roots are F, G, A and D (the IV, V, vi and ii chords in the key of C). By playing the root of each chord, we are assured of a strong melodic foundation upon which we can build lines. This also reinforces the thought process of thinking of the chord changes ie "vertical soloing."
Let's start by examining why notes are available in our old standby. The A minor pentatonic scale. A minor pentatonic is spelled A, C, D, E and G. As you can see, three of the chord roots the we need are available in this scale; the A, D and G. I'll demonstrate playing these notes as the chords progress and I'll simply rest when the F chord is occuring. Next I'll flesh out the solo with the A minor pentatonic scale, always targetting the chord roots. I'll continue to rest during the F chord. Next I'll add the F note for the F chord. Finally I'll "connect the dots" with the entire C major scale. The last portion of this lesson breaks down the progression into pairs of chords: F to G for measures 1 and 2, G to A for measures 2 and 3 and also measures 6 and 7, Am to F for measures 3 and 4, F to Dm for measures 4 and 5, Dm to G for measures 5 and 6, and measures 7 and 8 are Am. These five chord connections can be practiced as loops individually, then assembled together as your skill allows. This way you won't feel overwhelmed with the constant flow of chord changes. Remember that any progression can be viewed as the chord you're on and the upcoming chord.