Watch the Blues Walking Bass online guitar lesson by Mimi Fox from Flying Solo
The most important aspect of walking bass lines is the "feel"! While you are trying hard to "cop" my licks, remember to emulate the actual feeling and guitaristic nuances/dynamic shading that are happening. The technique will come if you practice diligently, but the FEEL of what I am doing is far more important. Listen closely! It's a good idea to practice developing strong bass lines WITHOUT chords first, then add the chords later.