Strumming Pattern:  DDU DDU(down, downslap, up, down, downslap, up)

That is how is should be played but I will show it my way first.

For now just do down strokes and I will update on how to do it the original way. This is 
just to give you an idea of how the song goes.

Do 4 down strokes, then three again and stroke G once then 4 down strokes for D then 3 
again and once again for G then back to A and restart the chords.

 A x4 A x3 G x1 D x4 D x3 G x1 A x4 etc
_____________
-----------3----2----2----3--------------|
-2----2----3----3----3----3----2---------|
-2----2---------2----2---------2---------|
-2----2------------------------2---------|
-----------2--------------2--------------|
-----------3--------------3--------------|