Riff 1: 
G|--------------------------------------------| 
D|--------------------------------------------| 
A|-5-7-----------------5-7--------------------| 
E|------0---0-7-5-3-5-------0-0-0--0-7-5-3-5--| 

Riff 2: 
G|-------------------------------------------------------------------------------| 
D|-------------------------------------------------------------------------------| 
A|-----------------------------------------------------------5-7 (Back to Riff 1)| 
E|-55555-0--0-0---77777-3-333-77---55555-0--0-0---77777-3-33---------------------| 

Play Riff 1 for the majority of the song. Listen to see when Riff 2 comes in.