Manners Question:

Sit up straight and lean slightly forward.
Sitting up straight and leaning slightly forward sends the following non-verbal signal: I'm listening intently. I'm interested in what you have to say. I have a lot of energy and I'm ready to go to work.
It's hard to believe that in a few seconds you can make this kind of impression, but it's true. So ignore this slice of interview etiquette at your own peril.