Be a good listener and listen carefully to the interviewer. Do not interrupt him midway. Ask for a clarification if the question is not clear. Think for a second or two before you answer and don't rush into the answer.
Speak clearly. Don't speak very slowly. Be loud enough so that the interviewers can hear you properly.
Be concise and to the point. Do not beat around the bush.
Be honest and do not try to fool the interviewer. If you do not know the answer of a question, admit it.
Don't get into an argument with the interviewer on any topic.
Never boast about your achievements. Don't sound overconfident or arrogant.
Project an air of humility and politeness.
Be positive and enthusiastic during the interview.
Maintain perfect eye contact during the interview. It is an indication of your self-confidence.
Feel free to ask questions if necessary. It is perfectly all right and much appreciated by interviewers.
Be natural and be yourself during the interview.