I'm off to an interview, care to share your last minute tips?

I have an interview in an hour and a half, I have everything, and I’ve got an outfit, a smile, and my awesome self. But I wanted some last minute pointers. It has been two years since I interviewed for anything.

Anything you got from firm handshake to complicated advice, I’m all ears.

Specifically, I am interviewing for a position as a saleswoman in an AT&T Certified Reseller…or something like that. Basically, I’ll sell phones and junk.