now here is what i just wrote to some dude who asked me for help:

to gain speed you say? well first off - speed is of no vital importance to music. having said that here´s the deal:

work on your right hand picking technique. at first you should get the tremolo technique done.
tremolo picking is basically just playing one note over and over again as fast as you can ( or as fast as the musical situation requires).
perform it by alternate pick the string as fast as you can. YOU CANNOT SHRED FASTER THAN YOU CAN PLAY THE TREMOLO except with tapping and sweeping! Your fastest tremolo is the limit.
you can push this limit by practicing the tremolo. use very little pick motion. practice the motion slow.
IMPORTANT: your picking motion should be THE SAME no matter at what speed you play. most guitarrists tend to make larger/different pick motions when they play slow.
there is a whole bunch of guitarrists out there who can play a fast lick but when you tell them to play it slowly they are like breaking their fingers.

there are basically 3 picking teckniques.
Alternate picking
Alternative picking (often also refered to as economy and sweep picking - economy picking in that case is basically a mixture of alternate and sweep)
Legato
with alternate picking you do a steady up and down motion. like this one (v = downstroke ^=Upstroke):


v ^ v ^ v ^ v ^ v ^ v etc
E||--------------------------------------||
B||--------------------------------------||
G||--------------------------------------||
D||-----------11-12-11----------11-12----||
A||--11-12-14----------14-12-11----------||
E||--------------------------------------||


With Alternative picking you do not change the picking direction when you change the strings. is called economipicking aswell because it requires less motion and it sounds a bit smoother.


v ^ v v v ^ v ^ ^ v ^ ^ v ^
E||--------------------------------------------||
B||--------------------------------------------||
G||--------------11-12-14-12-------------------||
D||-----------11-------------11-12-14----------||
A||--11-12-14-------------------------11-12-14-||
E||--------------------------------------------||

see?

an legato is basically just pick the first note on a string and hammeron/pulloff the other notes.


v v v ^ ^
E||--------------------------------------------||
B||--------------------------------------------||
G||--------------11h12h14h12-------------------||
D||-----------11-------------11h12h14----------||
A||--11h12h14-------------------------11h12h14-||
E||--------------------------------------------||

those are the 3 and you should practice all of them.

Whatever you practice - practice it SLOW!!! and practice with a metronome!!

keep your fingers always close to the fretboard. do not lift them off the fretboard more than a few millimeters. always use all 4 fingers, not only the first 3 like the bluesers from the 60`s. build up your speed gradually.
play as clean and precise as possible. there are heaps of shredders who noodle around the fretboard at blistering speeds, but half of it is only a formless blurr for they have a sloopy technique. you dont want to be just fast - you also want to actually hear all the notes you play. this can ONLY be acceived by practiveing slowly and precisely to a metronome using the above techniques. all the 3 techniques are equally important! develop a good left and right hand muting for you just want to hear the note you actually play without string noise from the other strings.

well.. i hope that will help you a bit