Thank the interviewer(s) in person, by email or by post. Common courtesy, alongside politeness really helps in interviews.
Make a good first impression, be polite with everyone you meet. Stand up, smile, make good eye contact.
Never be late. Make plans for all eventualities.
Don't just go over your CV. An interview is a chance to present all of your qualities that a CV can't present.
Read about popular interviewer questions and devise your answers. Test yourself beforehand with a few test questions.
Job Hunting Tips:
"Before you apply for any job, be sure to contact all of your references that you want to list and ask permission to do so. It’s always good taste to do so but it can also prepare the individual for when it happens. In most cases, you end up with a far better recommendation because the person isn't caught off guard, and they will have a chance to think of what they will say about you."