I assume you're talking about the main intro riff. The best thing I can tell you is just to slow it down to about 50% speed and practice the riff and pull offs so that you can do it cleanly without any other strings ringing out, then once you can do that consistently, speed it up in small increments until you get it up to the original speed. It's important that you don't try and practice it at a speed you can't do it comfortably at, because you'll just end up with messy bad habits. Start at the fastest speed you can play it well at and then speed it up little by little until you get it. It'll take time, but that's the point. Good luck!
