Having a professional binder on your lap is you can use it as a cheat sheet if you're nervous. Prior to your interview you should have a few key phrases written down to help you if you get stuck...and your short list of appropriate questions to ask them.

Lastly, you can keep handy your your professional references and copies of your resume in case they ask you for them. If a hiring manager asks you for your professional references during your interview, this is definitely a buying signal.