Research and preparation

• Learn as much as you can beforehand from your recruiter about the company and the position - size, products, corporate culture, reporting structure, responsibilities, career path, etc.
• Based on this research, prepare a list of intelligent questions
  

Non-verbal communication - dress, body language and eye contact

• Dress conservatively. Pay close attention to personal grooming - clean nails
  and hair, shoes shined, etc.
• Posture: sit up straight, keep your hands folded on your knees, briefcase or
  the arms of your chair. Lean slightly forward so as to convey an impression
  of alertness and energy
• Maintain steady eye contact with the interviewer. This does not mean
  staring - periodically look away, but always return your eyes to the interviewer especially when communicating

Communicate your strengths

• Match your responses to the requirements of the position, with the emphasis on your relevant skills and experience
• Conduct yourself with energy, enthusiasm and a positive attitude.
  Companies like to hire people with these traits!
• Be prepared to answer open-ended questions such as "what are your
  short/long-range goals?" "tell about yourself", and "what are your strengths
  and weaknesses?"
• Provide details and examples to underline your qualifications

Traps to avoid

• Never be critical of a former company or supervisor
• Don't tell long, rambling "war stories"
• Don't rush to answer every question immediately
• Control outward signs of nervousness - fidgeting, foot tapping, etc.
• Don't smoke or chew gum
• Avoid discussion of salary or benefits, at this point you are there to evaluate the position