There are many approaches to learning jazz guitar and by no means is this meant to be a definitive approach. However, in struggling to learn how to play I found some of the methods below helpful.
• Ear training with an aid; compare published versions of sheet music with your favorite recordings. This is a quick and easy way to learn how jazz players deal with various progressions
• Learn your favorite melodies in twelve keys. After a short time of doing this you get the feeling that your hand is automatically finding the right notes.
• Learn your favorite licks in twelve keys.
• Reduce chords to two and three notes. By simplifying the requirements for the left hand you can better focus on timekeeping and rhythmic content.
• Start ideas on all upbeats and the downbeats two and four. This will create more forward motion in the improvised line.
• Play triplets. This is not as easy as it sounds, especially if you have to cross strings. Guitarists are notoriously bad at playing triplets that are rhythmically accurate.
• Chord Melody: Many guitarists learn chord melody arrangements but get locked into one way of playing them. As with melodies practice solo arrangements in different keys.
• Play chords without roots when there is a bass player. Not always but often.
• Play chords with roots when there is no bass player.
• When working with a published transcription play along with the recording to match up with the time feel and articulation of the soloist.
• Do your own transcriptions of your favorite players.
Another simple thing I have found is that playing more horizontally than vertically on the guitar helps facilitate good articulation. When I started playing jazz I got stuck in 5th position as a result of playing scales through the cycle of 5ths in this position. Aside from wearing down the frets in this area this approach was not conducive to good articulation.
Please check out Warren Greig’s website at http://www.warrengreig.com/ to see what else Warren has to offer.