Watch the Mixing It Up online guitar lesson by John Goldsby from Upright Bass Handbook
Now let's play "Mixing It Up" at a faster tempo. Make sure you connect the notes and get a rhythmic flow from note to note. Concentrate on smoothly moving from one note to the next, and coordinating your left and right hand movements. The groove in a quarter-note walking bassline comes from the hypnotic, repetitious sound of the repeated quarter notes, combined with the up and down melodic contour of the line.
Once you have mastered this line, experiment with creating your basslines using chord tones, scale tones and chromatic leading tones. You'll discover some favorite devices that you like to hear when you improvise your own basslines.