E|---2--0-0---2--0-0---------0---------0----0------0------0------0------0---|
B|-00-00-0-0---00-0-0---30010-0--300110-0-----0-1-1--0-1-1--0-1-1--0-110-0--|
G|----------0--------0---------0---------0-2-2-2-2--2-2-2--2-2-2--2-2-----0-|
D|--------------------------------------------------------------------------|
A|--------------------------------------------------------------------------|
E|--------------------------------------------------------------------------|

So as you can see the first bit follows the pattern:
2x Riff 1 + 2x Riff 2 + Riff 3

The two parts with singing follow the pattern:
Riff 1 + Riff 2 + 2x Riff 1 + 2x Riff2 + Riff 3 (there is a little
embellishment here and there)

But on the very last time lose the last five notes of Riff 3 and
sustain the last '1' on the B-string. One other point is when you
play the '2's in Riff 3 sustain the note throughout the sequence.