This is a great little known Rory song (aren't they all all, unfortunatley) from his 
Jynx.

The song begins with a build up using the Am chord and this fill:

E---------------------------|
B--------------1------------|
G--------------2------------|
D---0h2p0------2------------|
A---------3~~--0------------|
E---------------------------|

Am                         (Fill)
From easy come and easy go,
Dm          G      C       (Fill)
Now you're not so carefree.
Am                                  (Fill)
You found the thorn behind the rose,
Dm            G      C    (Fill)
You took it, oh, so badly.

Chorus:
Dm
Lost inside yourself,
Am                           G/Am
You've gotta break out soon.
Dm
You've gotta try again
Am
To hear a brand new tune.
G
Oh Yeah...

Verse:
Once easy come and easy go,
You just hear sad notes lately.
You used to fly and chase the wind,
I don't know you lately.

Chorus:
Don't take it, oh, so bad,
Things are gonna change.
Don't make it, oh, so sad,
The sun will shine again.

(guitar solo)(use Am Pentatonic/C Major Scales - over the verse then chorus chord progressions)

Middle 8:

Please don't lock me out,
What's it all about?
I'll change it all completely.
Won't you let me in,
Don't you need a friend?
If I can help, just call me.

Verse:
I'm easy come and easy go,
Don't paint it all so sadly.
Before you know the light will shine,
Don't burn out completely.

Chorus:
Locked inside yourself,
You've gotta break out soon.
Come on and try again,
And hear a different tune

As for the bass guitar, Gerry MacAvoy bassicaly (GEDDIT?) plays the root notes of each 
but with the odd fill between notes - again play around in the above scales with it - 
music is all about jamming etc, so you dont have to be too accurate!

And thats about it! its a great chord progression for lead playing especially using the 
Pentatonic and C Major scales!

So just have a play about and enjoy!