When speaking face to face it’s said that over 90% of communication is non-verbal so before an interview, ensure you develop an awareness for what your body language subliminally says about you. 
Your body language should convey composure and confidence without being brash.
Ensure you make good eye contact and your handshakes are firm and clear and avoid excessive fiddling and jittering. If you feel your body language is not yet up to scratch, you can improve this by focusing on your outlook, identifying and embracing your strengths and feeling confident that you are knowledgeable in your interviewer’s values and ethics.
Overall, your body language should mimic an eager, confident and determined ‘can-do’ attitude without appearing arrogant.
Lastly, your interview attire and physical appearance must be professional, smart and current, avoiding anything overpowering!