Dont fall asleep. At least before they do. Offer them coffee and donuts. Tell them about how much fun it will be carrying a gun. Also, Randomly giggle, and break out in a nervous sweat. All those things will impress them, one way or another.
Really though, just be yourself and speak with them like they are a friend from long ago. Be respectful and to the point on every answer to thier questions. What departments are you applying to??