Interveiw advice needed! STAT

I have an interview with a nurse for a Doctor at a well known clinic. The doctor is a surgeon who does breast and other outpatient surgeries. I interviewed with the nurse manager and did great; I did ok with the doctor, but I was nervous and did not sell myself as I know I could have done! I have done some research and spoke with some doctor's who trained him; They gave me good references. So, I was called for a third interview with the nurses who work with him now. My question is, what can I do to secure my position in which I'm claiming? What kind of critical thinking questions do I need to look out for?