If someone told me this song was composed by O.P.Nayyar, sung by Mohd. Rafi and picturized on Shammi Kapoor, I'd have believed them(which probably goes to show I haven't listened to them as carefully as I should have).
The only problem I'd have with the music is that it is unoriginal. There's nothing bad about it but I wouldn't go out and buy a CD just to listen to this.
Musicwise, I suggest you get into more chords. Go beyond the majors/minors and get into extended chords. That helps a lot for a start.
Lyrics are nice. You've kept them simple.
Instruments mein there's really not much to talk about. It's just an acoustic guitar. Nice strumming I guess.
This song doesn't really suit you but you have the freedom of writing to suit your style. The problem with being inspired by bollywood is that it doesn't have much room for a voice like yours.
And surely you’ll buy your pint cup !
and surely I’ll buy mine !
And we'll take a cup o’ kindness yet,
for auld lang syne.