Watch the Spell It Out online guitar lesson by Jeff McErlain from Solo Factory: Chicago Blues
I love this lick and use it all the time. I am outlining an A7 chord and basically just playing the notes of a standard root 5 A7 chord, one of the first barre chords we learned. The final part of the lick is a little tricky as we are adding in some chromatic notes from B to G#. This lick can be heard countless times on blues records and should be in your bag.