Tips for wearing kurta correctly? (specifically about buttons)

I'm attending an Indian wedding for the first time (I'm American) and a friend helped me shop for a kurta for the sangeet. I noticed in the kurta shop that many of the advertisements of stylish men wearing kurtas had some of the top buttons unbuttoned.

In Western fashion, there are rules like to never button ALL of the buttons on a suit jacket; if you do you'll look like an idiot who doesn't know how to wear clothes. Now I'm wondering: Are there any such rules for kurtas? Specifically, any advice for buttoning all versus some of the buttons?