Intro
E|----------------------------|
B|----------------------------|
G|----------------------------|
D|----------------------------| x4
A|--8--8--8--6--4--6-6-^6/4---|
E|----------------------------|

than distortion kicks in play main riff

Main Riff 
E|--------------------------------------|
B|--------------------------------------|
G|--------------------------------------|
D|--------------------------------------|
A|--8--8--8--6--4--6-6-^6/4---8-8--8-6-4|
E|--------------------------2----2------|

quick side note:
the main riff sounds really good if you play it like so:

a|--8--8--8--6--4--6-6-^6-6-4---8-8--9-8-6-4|
E|----------------------------2----2--------|