This riff is used throughout the entire song:
  1 e + a 2 e + a 3 e + a 4 e + a
e-3-3-----3-----3-3-------3---3---|
B-3-3-----5-----3-3-------5---5---|
G-3-3-----3-----3-3-------3---3---|
D-5-5-----5-----5-5-------5---5---|
A---------------------------------|
E---------------------------------|

As you can see, the rhythm is very syncopated.  The right hand should keep strumming at 
constant pace while the left hand should be muting whenever notes aren't to play (the 
should technically have a bunch of X's throughout it).