Know the Employer
Do some research and try to find out as much as possible about the company to which you will be going for the interview.
Know what to expect
Never walk into an interview unprepared. Try to find out what sort of interview you will be expected to participate in. Interviews can range from a one to one interaction, to a panel of interviewers. At times you will also be required to sit for some form of test, such as Aptitude, IQ or Psychometric.
Be on Time
It is better to be a few minutes early than one minute late for an interview. Should for some unfortunate reason you are not able to make it on time, do make it a point to call to inform and apologize.
Dress Appropriately
If you are seeking a professional position, you must look like a professional. Dress as others do in the same profession. Remember, your first impression is a lasting one.
Know the Employer