If you are having a panel interview, try to keep an eye contact with the friendliest interviewer in the room. There is always one person who would not give you jitters and make you feel anxious, this will help you shine out in the interview and you will loosen up. Do not just keep sticking to one person, move your eyes around and make small contacts with other people in the room too, even if for little time. Otherwise they will feel left out and may mark you negatively.
One mistake that many applicants make is that they look away when a difficult question is thrown at them. You should not get confused and look away if you are asked a difficult question. Practice by standing in front of the mirror and watching your expressions. Eye contact does not mean that you cannot blink. Naturally you cannot look in one direction non-stop. When you move your eyes at different people, you will feel a little relaxed. You could also look at the interviewers hand instead of staring at his face all the time.
Do not feel scared and intimidated by the interviewer. You should know that you are an able person who can excel at his field. This will give you the boost needed to look the interviewer in the face and maintain eye contact. Eye contacts are also very important when you are shaking hand. Also when you emphasize your point during an interview, maintaining an eye contact will make the point stronger. Another time to make sure that your eyes are level with the interviewer is when he is talking, this will show that you are paying attention to what he is saying.