there's the signature riff of the song.  The best way to play it
is by keeping your pinky on the 7th fret of the A string the whole time and
using your ring, middle, and index fingers on the rest of the notes in
whatever pattern is comfortable for you.  But believe me, the pinky on the
7th fret creates a cool pedal-tone that sounds really close to the recorded
version.  Here's the riff:

E-|---------------------------||
B-|---------------------------||
G-|---------------------------||
D-|---------------------------||
A-|---7-7---7---7---7-7-7-7---||
E-|-0-7-7-0-6-0-5-0-3-3-5-3-0-||

Now, there's also a second guitar part played at the same time as the
signature riff.  If you listen close you can hear it.  It sounds quite a
bit like the following:
E-|-----0-------0--------0-------0---||
B-|---0---0---0---0----0---0---0---0-||
G-|-4-------3--------2-------0-------||
D-|----------------------------------||
A-|----------------------------------||
E-|----------------------------------||

Then, when the verses come in, there's this simple, 2 chord riff.  (If ya'
wanna get technical, I think the chords are F#5/E and F#5.)  I'm not very
good at writing it out "in rhythm" so just listen to the song and you'll
get the gist of it:
E-|----------------|------------------|------------------------||
B-|----------------|------------------|------------------------||
G-|----------------|------------------|------------------------||
D-|-4-4--4-4-x-x-x-|-x-4-4-4-4--4-x-4-|-(4)--4-4--4--4--x--x-x-||
A-|-4-4--4-4-x-x-x-|-x-4-4-4-4--4-x-4-|-(4)--4-4--4--4--x--x-x-||
E-|-0-2--0-2-x-x-x-|-x-0-2-2-0--2-x-0-|-(0)--2-2--0--2--x--x-x-||

Ah, but there's ALSO that cool ascending and descending harmonic thing,
right?  Right.  Well, all you gotta do is lightly touch the E string at
about the 3rd fret and pick 4 times (in rhythm) while gradually moving
your finger toward the 1st fret.  That's the ascending harmonic part; for
the descending, just reverse your direction.
   Ascending:         DEscending:
E-|-----------------||-----------------||
B-|-----------------||-----------------||
G-|-----------------||-----------------||
D-|-----------------||-----------------||
A-|-----------------||-----------------||
E-|-*3*-*2*-*2*-*1*-||-*1*-*1*-*2*-*3*-||
    (natural harm.)    (natural harm.)

Then, for the "chorus" ("I know you want what's on my mind..." etc.) it's
just standard power chords (5th's).  Here's how to finger them:
    B   A  D/A
E-|---|---|---|
B-|---|---|-3-|
G-|-4-|-2-|-2-|
D-|-4-|-2-|-0-|
A-|-2-|-0-|-0-|
E-|---|---|---|

And HERE's where they go:
B      A   D/A            A   B
I know you want what's on my mind,
B      A      D/A            A   B
I know you'll like what's on my mind,
B      A   D/A        A   B
I know it eats you up inside,
B      A    D/A
I know you know, you know, you know.


After the second "chorus", you go straight into this nifty riff.  It's a
simple moving-chord-shape.  I use my middle and ring fingers to do this:
E-|-0-0-0--0-0-0--0-0-0--0-0-0-0-0-0--0--0---0--0--0--0--0--0--0--0--0--0--0-|
B-|-3-3-3--5-5-5--7-7-7--9-9-9-9-9-9/11-11--11-11-11-11-11-11-11-11-11-11-11-|
G-|-3-3-3--5-5-5--7-7-7--9-9-9-9-9-9/11-11--11-11-11-11-11-11-11-11-11-11-11-|
D-|--------------------------------------------------------------------------|
A-|--------------------------------------------------------------------------|
E-|--------------------------------------------------------------------------|