The other version of this was totally wrong so thats why i've posted this one.

Intro/Main Riff
e------------------------------------------------------------------------------------|
B------------------------------------------------------------------------------------|
G------------------------------------------------------------------------------------|
D---------7-------7-7-------7-------10-10--------------------------------------------|
A-------5-------5---------5-------8--------------------------------------------------|
D---0h5-----0h5-------0h5-----0h8----------------------------------------------------|

e------------------------------------------------------------------------------------|
B------------------------------------------------------------------------------------|
G------------------------------------------------------------------------------------|
D-------7--------7-7--------7--------5-5---------------------------------------------|
A-----5--------5----------5--------3-------------------------------------------------|
D-0h5-----0h5--------0h5------0h3----------------------------------------------------|

Repeat this riff about 5 more times and then.... it changes very slightly.

e------------------------------------------------------------------------------------|
B------------------------------------------------------------------------------------|
G------------------------------------------------------------------------------------|
D---------12----------12-12----------12----------15-15-------------------------------|
A------10----------10-------------10----------13-------------------------------------|
D-0h10-------0h10-----------0h10--------0h13-----------------------------------------|

e-----------------------------------------------------------------------------------|
B-----------------------------------------------------------------------------------|
G-----------------------------------------------------------------------------------|
D---------12----------12-12---------12--------10-10---------------------------------|
A------10----------10-------------10--------8---------------------------------------|
D-0h10-------0h10-----------0h10-------0h8------------------------------------------|

h=Hammer on (slur) - These notes may or may not be slurred, it's hard to tell exactly, 
it sounds correct to my ear.