Walk into the interview with confidence through strong posture and a firm handshake. Make eye contact with the interviewer and those in the room while asking and answering questions. Sit in a relaxed but engaged manner with feet and knees pointed towards the interviewer. Avoid fidgeting or playing with objects. Use limited hand gestures to emphasize points but don't overdo it. Lean forward in the chair at appropriate times to demonstrate interest without appearing overly confident.