Watch the Voice Leading Applications online guitar lesson by Kenny Wessel from Shades of Jazz
Voice leading is a very important skill to have when playing melodies over chord changes. I consider it to be an organizing principle of my approach to playing and teaching as it allows a musician to create smooth, singable, musical lines over chord progressions. Guitarists are notorious for bad voice leading because of the visual shapes and grips that many of us gravitate towards, instead of visualizing how the notes change when the harmony changes. As many of us visualize the fretboard in patterns and shapes, its challenging to approach the guitar more musically, and see how the scales and keys relate to each other from the inside (from note to note), but its essential that we do this if we want to develop and deepen our playing and improvising.
A good guideline to strong voice-leading would be to not move more than a whole step between pitches when chords change. This can always be done w/ any two scales! Many beginning improvisers switch positions or jump back to the beginning of a scale or pattern when chords change. Try to connect the chords by not moving more than a whole step as the progression changes. You can also stay on the same note, play a common tone to both chords/scales, if that note is in both scales. It's also important to be able to play the different scales without moving up or down the fretboard more than a fret or so. If we can visualize both scales in one position or area, this will open up the fretboard and allow us to connect our phrases and play more musical lines.