Watch the Lower Leading Tones online guitar lesson by John Goldsby from Upright Bass Handbook
Using three leading tones from below into the root of a chord is a great way to outline the root motion of a chord progression. Once you become comfortable anticipating a root and approaching the note from above or below, then you'll never have problems playing a walking bassline.
Use your ears to tell you which notes sound correct. Keep your right and left hand in a comfortable position, but make sure you are accurately coordinated with both hands.