Metronome + picking fast licks you want to play + years of practice.
Whatever you do, don't sit and do chromatics for hours and hours no matter what someone tells you. They're good for finger independence but that's about it. Here's some I started with:
------------------------------------------------------------5-6-8-5-6-8
------------------------------------------------5-6-8-5-6-8------------
------------------------------------5-6-8-5-6-8------------------------
------------------------5-6-8-5-6-8------------------------------------
------------5-6-8-5-6-8------------------------------------------------
5-6-8-5-6-8------------------------------------------------------------
------------------------------------------------------------8-6-5-8-6-5
------------------------------------------------8-6-5-8-6-5------------
------------------------------------8-6-5-8-6-5------------------------
------------------------8-6-5-8-6-5------------------------------------
------------8-6-5-8-6-5------------------------------------------------
8-6-5-8-6-5------------------------------------------------------------
------------------------------------------------------------5-7-8-5-7-8
------------------------------------------------5-7-8-5-7-8------------
------------------------------------5-7-8-5-7-8------------------------
------------------------5-7-8-5-7-8------------------------------------
------------5-7-8-5-7-8------------------------------------------------
5-7-8-5-7-8------------------------------------------------------------
------------------------------------------------------------8-7-5-8-7-5
------------------------------------------------8-7-5-8-7-5------------
------------------------------------8-7-5-8-7-5------------------------
------------------------8-7-5-8-7-5------------------------------------
------------8-7-5-8-7-5------------------------------------------------
8-7-5-8-7-5------------------------------------------------------------
16th note triplets of course, basically just works the 1st, 2nd and 4th finger then takes it in reverse, goes to 1st, 3rd and 4th finger then takes it in reverse. Add some finger spacing to the first pattern, move it down to the 11th fret and you've got the first run from the CFH solo:
------------------------------------------------------------------------------------------11-12-15-11-12-15
------------------------------------------------------------------------11-12-15-11-12-15------------------
------------------------------------------------------11-12-15-11-12-15------------------------------------
------------------------------------11-12-15-11-12-15------------------------------------------------------
------------------11-12-15-11-12-15------------------------------------------------------------------------
11-12-15-11-12-15------------------------------------------------------------------------------------------
I've found those to be the most helpful exercises... unless you want to go crazy with pentatonics ala Zakk Wylde:
8-5-8-5-----8-5-8-5----
--------8-5---------8-5
-----------------------
-----------------------
-----------------------
-----------------------
16th note triplets, then I start goin' higher up just following the A minor pent or move it to whatever key you're in... another common one:
8-5--------------------------------------------
----8-5-----8-5--------------------------------
--------7-5-----7-5-----7-5--------------------
--------------------7-5-----7-5-----7-5--------
--------------------------------7-5-----7-5----
--------------------------------------------8-5
16th note triplets again... those help me out anyway. Pick some that you like, no point learning it if you're never going to use it again IMO. The reason I chose those is 'cause they're pretty common patterns so they came in handy later down the road.