Watch the Take Your Time online guitar lesson by Jeff McErlain from Essentials: Advanced Blues Rhythm
This tune is basically the same riff as Otis Rush's "It Takes Time" which is a great tune similar to "Checking on My Baby" by Sonny Boy Williams, which is similar to many blues tunes. I took the approach Fleetwood Mac does to the tune, which is a little heavier. Anyway you cut it, it's basically the same groove, and equally essential.
This is called "The Uptown Shuffle". VERY IMPORTANT lingo there. On a gig, I can call out the tune and say it's an uptown shuffle and they'll know it's basically this riff. Root, 5, b7, and root each double picked. If there's a downtown shuffle, you know it's the root, go-up-the-octave, b7, and 5, each double picked. See, it pays off to read these comments because I didn't put this info into the video!