Intro:
-----15--------16--------13--|
---15------14--------12------|
-15----------15--------14----|
-----------------------------|
-----------------------------|
-----------------------------|

Main Riff:
--10h11----10----------------15-----------------13--------13-----|
-10----10------------15--15-----------13h14p13----14--14----14---|
---------12------------15--15-----------------15----13--13-------|
-----------------------------------------------------------------|
-----------------------------------------------------------------|
-----------------------------------------------------------------|

This is about it.  He changes the riff a little each time by adding notes
between the three parts (same chords though), but the lead note of each part
stays the same (to match the singing.)