Be particularly clear on what you know and what you want to achieve:

If your interview is resume-based (you've had to supply a resume either before or concurrently), have the facts of your stated objective, relevant experience, education, etc. thoroughly memorized and mentally supported. As to your job objective, be clear on what you want, as well as what you don't want. There's little room in the job market for the applicant who's willing to take anything; he or she will usually get nothing!

From: http://topten.org/public/AB/AB8.html