how one interacts with people, how one presents him/herself etc, are also important during interview. Often times, there are more than 1 people quanlify for the position, technically, but an interviewer also looks for people who can fit in better. Confidence is important, but should not be over-confident, or too casual.  I have interviewed people who asked me personal questions during interview, which was quite unprofessional. Try to think of ways to keep conversation going beforehand.