eye contact is a main thing. and try to be as comfortable as possible and make it into a conversation. stay sitting up, dont crouch. try to avoid "um's" and "uh's". be honest because they can see through liars.
anyway! i had an interview once at old navy, and the lady asked me if a family member or someone i knew stole from the store if i would tell. and i said no. i didnt get the job
what the hell, if i was to say yes they would know im a dam liar. IT WAS A LOSE/LOSE SITUATION. stupid.