Got My Mojo Working - Blues Standards
It's important to spend time on this standard due to the fact that it's commonly called as the last number of the night. I can't tell you how many times this song was called at the end of a harmonica blowout.
There are two common approaches harmonica players can take...
The easiest is the call and response horn line that James Cotton uses, which is 2 2 2 (2 draw... the root note played three times) after each vocal line of Muddy. This is simple, but catchy and effective. When on the V Chord (bar 9) improvise a V-IV-I lick and turnaround.
The other approach is Little Walter's, and of course is more complicated. He plays a draw slide down to 1 draw and then 2" 2. The IV Chord he plays the slide to 1 draw to 2" and instead of 2 he plays 3' (flat-7th of the IV chord). The challenge of this approach is that there are tons of inhale notes, making this a very difficult way to play in regards to breathing.
If you woiuld like to explore these approaches take a look at the "Accompaniment Study 8 - Hooks" (http://www.bluesharmonica.com/lessons/accompaniment_study_8), specifically examples 2.1 and 2.2.