I love this song- it's from the new moon soundtrack.
Play the Bb/G like this:  
e | ---3------------------- | 
B | ---3------------------- | 
G | ---3------------------- | 
D | ---3------------------- | 
A | ---1------------------- | 
E | ---1------------------- | 

Intro: ~ F5  Bb5  Bb5  C5  F#5  F5 ~

Verse:

Bb5         Bb5
All of the astronauts
             C5
Champagne in plastic cups
        F#5          F5       Bb5
Waiting for the big hero to show.
Bb5          Bb5
Outside the door he stands
         C5
His head in his hands
        F#5           F5
and his heart in his throat.

Chorus:

Eb5          Bb5
What can he tell them now?
Eb5      C5
Sorry I let you down
Eb5       F5            Bb5
Sorry it wasn't quite true.
    Eb5        Bb5
But don't get hung up on it
Eb5           C5
Just soldier on with it.
    Eb5             F5            Bb5
And good luck with shooting the moon.

Repeat for other verse and chorus.
Enjoy!