Here is the arrangement I use. Played it for a friends wedding and it seemed to go down well anyway.

If You Stay

Capo 3
All chords relative to capo
INTRO (G)

VERSE 1 (G – Em7 – C – G)
In the window down the meadow,
A path of silver moonbeam,
Slips through winter snowflakes,
Like a dream.

VERSE 2 (G – Em7 – C – D – G)
Our small hearthfire,
Warms the world tonight,
And I get to thinking you and me,
Maybe we could better make our way,
If you stay.

CHORUS (D – Em7 – C – D)
I need your simple healing touch,
Need your power need your love,
Inside me to guide me,
I know it won't be easy,
But I promise to be with you,
Come what may.

VERSE 3 (G – Em7 – C – D – G)
If you stay here, there'll be no fear,
If we bend we'll never have to break,
We'll work things out and it'll be ok,
If you stay...

String section (Em7 – C – G)

CHORUS (D – Em7 – C – D)
I need your simple healing touch,
Need your power need your love,
Inside me to guide me,
I know it won't be easy,
But I promise to be with you,
Come what may.

(G to end)
If you stay...

(N.b Em7 fingering is 024030)