**** EDIT ****
3Aug12:
Well, crap! I just visited justinguitar.com to review and move on to the next stretch in the exercise and found that what I posted above was incorrect. That is, while Justin's lesson TE-001 is titled "Finger Gym" that's not the one I practice to increase my stretch (and dexterity and strength).
The correct lesson number is TE-007 and is found here; http://justinguitar.com/en/TE-007-FingerStretch.php Amazingly, he calls it, "Finger Stretch Exercise". The other posted above looks worthwhile too and I'll get to it someday...
Sorry 'bout that!
Last edited by john of MT : 08-03-2012 at 06:03 PM.
A nice warm up is also to play the scales of a particular key using only legato, hammer on's and pull off's.
This way you are doing good left hand practice but also you are learning or reenforcing the scale shapes whcih will be very handy.
I always believe that chromatic stuff is really not the best way to go about things since it is limited in application and also doesn't provide the technique practice one thinks it will.