"baat pakki"

The parents usually begin by saying, 'ji bachon ki khushi se barh kar kuch nahin.... :)'
larke wale invite the girls side or they invite you..whichever way you are comfortable with....and they express their love and khushi....showering the girl and the guy...with achi achi batein...:) ..like 'bohat khushi ki baat hai...etc etc.....' or you dont have to be too formal....

the guys's mom puts karey on the girl....which I think is the most appropriate piece of jewelery for the baat paki time...lol :)
you can give a nice suit to the larki's mother or if you want even a small gold gift....not too overwhelming...and not too distant.... :)
you can also take mithai...cake...cupcakes...