Applied online, contacted about a week later to interview 1:1 on campus. The interviewer was very friendly. He explained that the interview was "behavioral" and all questions followed the format of "tell me about a time when X and how you responded to that." The final question was supposed to test your ability to think on your feet. I was asked to choose one of four broad topics that I know nothing about, and then I was asked a series of questions about that topic -- what are the advantages and disadvantages of X? etc.