Just be yourself. Display energy and show sincerely you are interested in the job.
Be ready for a single or a panel interview. A panel interview consist of 2 or interviewers conducting an interview with you. On the other hand, there are also cases that applicants are being interviewed simultaneously in one room. This is quite challenging since you will be face to face with your competitor applicants and everybody would hear your answers.
Watch your grammar. Articulate candidates makes an edge with others who cannot express themselves fully and with clarity. Use pauses rather than "uhs".
Watch non-verbal communication. Pay attention to your posture, remember that you are making a good impression to your future employer. Do not appear to be over relaxed or too rigid. If the interviewer moves his/her chair back, check your posture. You may be leaning forward too closely. Sit back in the chair instead.
Be alert and attentive. Be sure you understand the question. If you don't, ask for clarification. But once is enough, it is embarassing to ask the interviewer to repeat the questions again and again. It would make a bad impression on you or she/he maybe annoyed by it.
Be prepared to answer tough questions. Be ready to answer in depth information from your resume and some tricky questions to test thinking ability. Stress your qualifications that give clues to your interviewer that you fit the requirements.
Never criticize a former employer or the company itself. No matter how bad experience you may had with your previous work, do not elaborate or say things against them. It will give a wrong signal to your future employer that you will do the same thing on them in the future.
After the interview, leave politely and jot down the pertinent questions you remembered during the interview. Evaluate yourself and learn something from it for your development.