My two cents. I've interviewed a lot of law clerks the past few months, and in my recent experience it's easy to tell when someone is not being genuine. I was probably guilty of handing out some "lines" when I was the interviewee and thought they were brilliant. They weren't. Being truthful, open, and honest is the best way to go. Try and treat it like a natural conversation, and the interviewer should understand you might be nervous. It helps to have done a little "homework" on the place you are interviewing and I always appreciate when people seem to actually know what we do. It shows you care enough to do more than just show up. Finally, always have a specific question or two to ask at the end.