This exercise will help with changing keys smoothly, and with moving around the fingerboard easily and efficiently.
Start in the key of C and improvise straight eight notes at a reasonable tempo. For now DO NOT LEAVE THE KEY, but stay in C, playing only scale tones. Try to use different melodic patterns and to shift smoothly from position to position.
A few words about fingering….
While fingering is a huge subject, a basic few tips are useful at this point.
ALWAYS play on the tips of the fingers.
Keep your wrist only very slightly bent away from the fingerboard, with knuckles straight in line with your hand.
When ascending try to shift from 3rd or 4th to 1st or 2nd finger, so that you always have somewhere to go.
When descending shift from 1st to 2nd finger or 3rd or 4th.
Once you feel pretty comfortable with Perpetual motion in C, try shifting between the keys of C (No flats or sharps) and F (Bbs in the key), still playing straight eight notes at a reasonable tempo. As you will have noticed by now, changing keys from C to F only involves changing Bs to Bbs. DO NOT shift or leap to the next key, but make sure to continue smoothly in the same direction when you change keys. You might also try to keep a melodic pattern ascending or descending while changing keys. Next try shifting between F and Bb (Bbs stay and Es becomes Ebs). Once you can do this try perpetual motion between C, F and Bb.
Add keys slowly until you can shift smoothly between all 12 keys. At first this may seem impossible, but if you go slowly, step by step, you will come to visualize the common tones between keys easily and effortlessly.
The whole process can take a student from 2-6 months of hard work, so don’t be discouraged or overwhelmed. Steady practice is all that is required. If you find yourself away from your guitar with time to kill, try practicing in your head. VISUALIZE the fingerboard and go through different scales, fingerings and all. Don’t underestimate this kind of practice as it is some of the best study one can do. The clearer your mental image of the guitar, the easier it is to play what you want to.
AFTER you are pretty fluent with major scales, flat the third on ALL OF THEM, and you have your melodic minor scales. Then you can go through the entire study again, this time learning melodic minor scales. Of course since by now you are pretty good at major scales, learning these will go much faster.
….and when that is done take all your melodic minor scales and FLAT THE 6 to get all the Harmonic Minor Scales….HA! This ought to keep you off the streets for a while.