Main Riff:
 E |----------------|----------------------------|
 B |-------9-------7|----------------------------|
 G |----------------|-------9-------9-------9----|
 D |----9-----9-9---|--9-7-----7-7-----7-7-----7-|
 A |-7--------------|----------------------------|
 E |----------------|----------------------------|

2.This is the 2nd way you can do it, it also sound cool..:
 E |-------4-------2-|---------------------------|
 B |-----------------|-------5------5-------5----|
 G |----4-----4-4----|-4--2-----2-2----2-2-----2-|
 D |-2---------------|---------------------------|
 A |-----------------|---------------------------|
 E |-----------------|---------------------------|

All the Verses:
(Use Lightish to harder Distortion)
Do "part 1" then sing "Dont want to grow up" then "part 2"
and then "thats wishfull thinking"
The whole time he sings between guitar strums.

"Part 1" "Part2"
 E |------------------==-------------|---------------------------------|
 B |-x-x-----------------------------|---------------------------------|
 G |-x-x-----77--------99------------|---------------------------------|
 D |-x-x-----77-Dm-----99-Em---------|------x-x------9-----------7-----|
 A |-x-x-----55--------77------------|------x-x------9--Bm-------7--Am-|
 E |---------------------------------|------x-x------7-----------5-----|

Prechorus:(when going into the Pre chorus,slide from Am)

 Gm  Am  (These chords are muted and occasionally released
according to your own style)
 E |------------------------------------|
 B |------------------------------------|
 G |------------------------------------|
 D |-7-⁄5-5-5-5-5-5-5-5/7-7-7-7-7-7-7-7-|
 A |-7-⁄5-5-5-5-5-5-5-5/7-7-7-7-7-7-7-7-|
 E |-5-⁄3-3-3-3-3-3-3-3/5-5-5-5-5-5-5-5-|

Chorus..

"18 till i die,Gonna be 18 till i Die",Ect
Strumming is not indicated, but its just A basic,  D  G  Em  Asus2
proggression.. Its all distorted, just sing while strumming 
these chords and you will get it!!

 E |-----------------------------------------------------|
 B |---------------------------------------------------0-|
 G |-7---------------------3-------------0-------------2-|
 D |-7---Dm----------------5-------------2-Em----------2-|
 A |-5---------------------5---Gm--------2-------------0-|
 E |-5---------------------3-----------------------------| 

 Intro: B  B  G#  F#  B  F#  E  B  E  E  E  E  E  E 

Verse 1:
 E  A 
I wanna be young the rest of my life;
 E  A 
Never say no, try anything twice.
 E  A 
'Til the angels come and ask me to fly,
 E  A 
Gonna be 18 till I die
18 'til I die!

Verse 2:
 E  A  D 
Can't live forever, that's wishful thinkin'.
 E  A  D 
Whoever said that must have been drinkin'.
 E  A 
Don't wanna grow up. I don't see why.
 G  A 
I couldn't care less if time flies by.

Chorus:
 D  G  D  A 
18 'til I die, gonna be 18 'til I die.
 D  G 
Yeah, it sure feels good to be alive,
 D  A 
Someday I'll be 18 going on 55.
 D  G  A 
18 'til I die.

Verse 3: (same as verse 1)
Anyway, I just wanna say
Why bother with what happened yesterday?
It's not my style, I live for the minute;
If ya wanna stay young, get both feet in it.
18 'til I die.

Verse 4: (same as verse 2)
A little bit of this,a little bit of that;
A little bit of everything, gotta get on track.
It's not how you look, it's what ya feel inside
I don't care when, I don't need to know why.

Chorus:(same as before-different ending)
 D  G  A 
...18 'til I die. There's one thing for sure,
I'm sure gonna try.

Then you play the chorus again without words(instrumental):
D  G  Em  A  D  G  Em  A 

ENDING:
Yeah don't worry about the future, forget about the past;
We're gonna have a ball, yeah, we're gonna havea blast.
Gonna make it last. Hey, yeah.