riff 1
E|--------------------------------------------------------------------|
B|-------6-----------6--------------------------6---------------------| 2x
G|-----7---7-------7---7-5-7-8----------------7---7--10-8-7-8---------|
D|-5-8--------5-8--------------8-7-8-7----5-8-----------------8-7-8-7-|
A|--------------------------------------------------------------------|
E|--------------------------------------------------------------------|

riff 2 - it's hard 

riff 3  
E|-------------------------------------|
B|-------------------------------------|
G|-------------------------------------|
D|---------6---------7-----------------| 4x
A|-6-8-6-8---8---6-8---8-9-8-9-8-6-----|
E|-------------------------------------|

Riff 4 like riff 1 but with some minor change in the end
E|-------------------------------------------------------------------|
B|-------6----------6--------------------------6---------------------|
G|-----7--7-------7---7-5-7-8----------------7---7--10-8-7-12-8-7----|
D|-5-8--------5-8-------------8-7-8-7----5-8-------------------------| 2x
A|-------------------------------------------------------------------|
E|-------------------------------------------------------------------|

0:00 - 0:33  riff 1
0:33 - 1:07  riff 2
1:07 - 1:37  riff 1
1:38 - 2:11  riff 2
2:11 - 2:42  riff 3
2:42 - 3:15  riff 2
3:15 - 3:46  riff 3
3:46 - 4:20  riff 4