Intro:
C

Verses:
C, but taking your middle and index fingers off the fret board in on alternate strums.  
really doesn't make sence, sorry, just watch the video)

Chorus:
Dm & Am

At 2:09 in the vid:

E|--------------------------|
B|------1-------1------1----|
G|--------2------2-------2--| etc...
D|----2-------2------2------|
A|--0-------0------0--------|
E|--------------------------|