Intro
G------------
D------------
A--5-------3-
E-------1---- (x4)

Verse (let each note ring)
G---------------------
D---------------------
A------5----1----3----
E-1------------------- (x2)

Bridge (let each note ring)
G---------------------
D---------------------
A-1----5----1----3----
E---------------------

Chorus
G-----------------
D-----------------
A-55--11------33--
E---------11------ (x3) 

Chorus Pt 2
G---------------
D---------------
A----------1----
E-33333333------

Ending of chorus
G------
D------
A------
E-1----

Verse (x2)
Bridge
Chorus (x3)
Chorus Pt 2
Ending of chorus

Break (let each note ring)
G---------------------
D---------------------
A------5----1----3----
E-1-------------------

Bridge
Chorus (x3)
Chorus Pt two
Chorus (x3)
Chorus Pt two

That's it! 
Great Song, isn't it? 
Rate it, 'cuz it is easy and I think that's 
exactly how Avrils bassplayer plays it!!!