Dress neatly and professionally. Never forget that first impressions count and this initial impact will always be judged on how you present yourself.
Smile broadly and give a firm and confident handshake.
Speak clearly and confidently and always maintain eye contact with the interviewer. Try to look relaxed and calm.
Listen carefully to the questions asked by the interviewer and do not interrupt or veer off-topic. Do not waffle as this is a common reason for being turned down for a job.
If a question is awkward or difficult – take your time before answering. If you need clarification before you answer that is often a good sign and is expected. If you really don't know the answer, say so. This is better than making it up.
Avoid asking too much about the salary or package – ask about the role at this stage.
Display interest in the role and ask plenty of questions.