Agreed with Jd as far as practice (I gotta start doing all that. grr...bad tap!) but, for warmup if I get shotgun dragged onto stage for a jam, or am cold for some reason, I use this...
Fingering corresponding to frets below:
G|-1---2---3---4---|
D|---3---4---1---2-|
Do not release any frets before you bump the pattern up a half step, maintain pressure even after you've played the notes. Walk it up to the 12th fret in the same pattern, then skip one string:
G|-1---2---3---4---|-2---3---4---5-----|-> etc
D|--------------------------------------|
A|---3---4---1---2-|---4---5---2---3---|-> etc
Then skip two strings, etc etc. Can run it on the interior, starting with D or A - but make sure it's comfortable. Serious attempts from C to B on a 6 is very not suggested unless related to Andre the Giant(RIP). G to B on a 5 is fine with lots of practice.
Generally, I run it through all the string skips off whatever top string I have on me (G-D G-A G-E). Two of the runs with fingers, one with double/triple thump, maybe one of octave taps if I feel the need, and both hands are nice and warm when I get up.
Very spidery, esp on the 2+ skips. Gorgeous for forcing proper left hand position, as you can't play it clean without your thumb being anchored in the right place. Improves stretching, strength, coordination, precision and speed. Makes some of the girlies go "ewww...." then they go, "hrmmm...."
Just make sure you have clean fingernails.
But, this exercise don't do a damn thing for your ear...
