(easier to start on the high e string)
and like g.god420 said...go at a slow tempo
till you can play it cleanly and solid...
only then...speed up
(highly suggest using a metronome)
to build a very strict right hand
(if you dont got one..you can download one)
and warm up your hands..dont mess em up
if you feel pain...STOP and check it out.
do the 1234321234 like he said..then
take it up to the b string.
then keep goin up..to the low e
its really a good exercise in frethand/pickinghand
coordination.
then switch it up a little
1324(slide up a fret) 2435..slide up a fret...3546..etc..
(all the way up the neck..then back down..)
and just a little comment.(may seem small and trivial but
not meant to talk smack)
but its down up down up
(start with down stroke)
later on when you're really smooth, you can start
with upstrokes..
(im assuming you're a beginner so it's better to
go down up down up)
yo