B
E|----------------------------------| This is the main riff, used
B|----------------------------------| through most of the song.
G|----------------------------------| Have your index finger barre
D|--9---7-----------------7---------| the 7th fret.
A|----------7h9---7---7h9-----------|
E|-7---7---7-----7---7--------------|
           ^^^
            Very quick hammer

   E
E|--------------------------| Then it shifts up to the key
B|--------------------------| of E...
G|--9---7-----------------7-|
D|----------7h9---7---7h9---|
A|-7---7---7-----7---7------|
E|--------------------------|
           ^^^
            Very quick hammer


  F#
E|--------------------------------------| Now down to F sharp (Barre
B|--------------------------------------| the 2nd fret)
G|--------------------------------------| Play a quick E5 after doing
D|--4---2-----------------2-------------| this riff once, then go
A|----------2h4---2---2h4---------------| back to the key of B.
E|-2---2---2-----2---2------------------|
           ^^^
           Very quick hammer


There are a few variations to the basic riff.  Right before the solo,
when the rhythym guitar plays alone, you hear this:


E|----------------------------|
B|----------------------------|
G|----------------------------|
D|--9---7------------------7--|
A|----------7h9---7---7779----|
E|-7---7---7---7---7----------|
           ^^^
            Very quick hammer


Lastly, during the outro solo, you hear this variation:

E|--------------------------------|
B|--------------------------------|
G|--------------------------------|
D|--9---7-------------------------|
A|----------7h9---7--12-11-10-----|
E|-7---7---7---7-----10-9--8------|
           ^^^
            Very quick hammer