Research

Prepare beforehand:
  1. Bring your resume with you and be prepared to complete an application before or after the interview. 
  2. Know where you are going plan to leave early.
  3. Do some online research of the client's industry and determine what is typically expected of people in the role you are interviewing for.
Know what you are talking about:
  1. How big is the company in terms of its competitors by annual sales or employees?
  2.  What does the company say about its products or services?
  3. What recent news (such as a new product, a press release, an interview with the CEO) can you discuss? 
  4. If the company is public, the boilerplate at the bottom of its press releases will tell you a lot.