When you sit, place your bag on the floor so it does not become an obstruction between you and the interviewer. If possible, angle the chair at 45 degrees so you can lean toward the interviewer as you speak without seeming like you're staging a frontal attack. If you did not send the interviewer a resume before the interview, this is the time to present it. When seated avoid pressing your knees and ankles together like a frightened child. Both moves make you look relaxed and also show subtle acceptance of him or her.
Few people like to feel physically threatened by a stranger.
OPEN UP One point about interviewing which you may overlook is remaining in touch with your own feelings going into and during the interview. If you stop to think, you will realize that you have far more power during the interview than you believe. It is you, the interviewee, who initiated the interview. If it becomes apparent during an interview that the firm has nothing to offer you, you can relax and use the opportunity to learn more about the field in general, about the interviewer's own background, and about what he or she thinks of things in general. The one thing you must gain from each interview is new knowledge and, perhaps, new contacts.