Be honest and be yourself. Your best professional self. Dishonesty gets discovered and is grounds for withdrawing job offers and for firing.
DO'S
Don't make excuses. Take responsibility for your decisions and your actions.
DONT'S
Don't make negative comments about previous employers or professors
DONT'S
Don't treat the interview casually, as if you are just shopping around or doing the interview for practice. This is an insult to the interviewer and to the organization.