How to get a smaller waist with proper dressing style?

I am in my late teens, and I am not really thin, moreover, I have a boyish body type. I want to know if there is any particular way of dressing up for a prom party to give my waist a smaller look. I am following a healthy meal regime, and do crunches for exercising as well, but I believe the results would not be evident at this party, which will be held this weekend! Can somebody please assist appropriately on how to get a smaller waist for the party? Thanks.