Agree with edw519 entirely. I should add that we always arrange for a sightseeing tour and meals with interview candidates in order to facilitate talking on a variety of subjects. These activities are chaperoned not by the people who will interview them, but people who would work with them if they got hired. We also give them interview tips, and brief them on the background and style of the people who will interview them. The best interview is one without surprises.

(We're not google, we only shortlist 4 people at a time, and hire rarely, so we can afford to take the time).