Watch the G Man online guitar lesson by Jeff McErlain from Essentials: Solo Electric Blues
I love this tune as it has so many cool things going on starting with the a descending octave bass line. Like any tune you learn, just get the notes down first, then break it up into sections to help perfect each part. The bass line on the top of the song uses an unusual picking technique where we essentially pull the string up with the thumb and let it smack against the fingerboard. It's a little like slap bass, but cooler. ;-). Don't be afraid to really pull that string, you won't hurt the guitar and it adds a great percussive sound that acts a little like a drummer. As you can see there are two variations of the line, feel free to mix them up. I have stolen this line and placed it in many songs in open G. Although not a straight blues, it is still a blues that uses the I7, IV7, and V7 chords. Make note of the fingerings as you will see them in just about every blues in open G.