Multiple interviews tend to be redundant, tiring, and sometimes irritating. The first ninety seconds - enthusiasm, confidence, smile. You are interviewing too. Use waiting time to talk to secretaries, receptionists, etc. They can sometimes tell you a lot.
Secretaries can be a great ally for future contacts.
Talk to them. Be consistent in your answers to repetitive questions. If interviewer gets involved in long phone call, indicate that you will leave if it is confidential. Get names and titles of interviewers as you go. Often the more important decision makers are at the end of your schedule.