To play this blues classic you’ll need to tune your guitar to Open D. To do this you’ll tune the guitar to DADF#AD. Much of the song is played with a slide on your pinky finger (4th finger). Lay your other fingers softly on the strings behind the slide to help prevent unwanted noise.
Measures 1 thru 4 and measures 7 and 8 are played completely with the slide while measures 5, 6, and measures 9-12 are played without the slide.
With your guitar tuned to Open D, strumming the strings open will produce a D chord:
Measures 1 and 2 give you a good idea of the slide work that is to be expected throughout the riff:
Measures 5 and 6 don’t require the slide, so we just hold our slide finger up out of the way.