Watch the Blues Riffs for Duke online guitar lesson by Frank Vignola from Essentials: Jazz Standard Soloing
This 12-bar blues in C starts with a C chord, then to the 4 chord, F7, and back to the C. Going over the chord tones, we notice the main difference between the C and F7 is that the E note (the 3rd of C chord) becomes an Eb (b7 of F7 chord) and then back to the E (3rd of C). So, we use this difference in the riff. We also use the 2-5-1 to get back to the 1 chord. Instead of just ripping off pentatonic scales, the idea here is to use that difference between chord tones (the E and the Eb). Notice the Q/A, the slide into the first E note, and the ending phrase over the 2-5-1.