This isn't how it's meant to be played, but I personally think this sounds better.

|--------------------------------------------------|
|--------------------------------------------------|
|-4-4----------------------------------------------|
|-4-4--4/6-6--6-6-6--6/8-8--8/9-9--4/6-6--6-6-6--6-|
|-2-2--4/6-6--6-6-6--6/8-8--8/9-9--4/6-6--6-6-6--6-|
|------2/4-4--4-4-4--4/6-6--6/7-7--2/4-4--4-4-4--4-|

The riff's repeated throughout the song, but mainly heard at the intro. As I said, I 
prefer to play this version, it's deeper, rougher and easier to play.