I got the first round on-campus interview, and trading group manager give me an interview. Questions are cliche, but you definitely need to do your homework. There are four parts of the interview: Competence, motivation, and ethic (There should be one more, but I forgot sorry guys)
By the way, before the interview, BP also hold a preinterview dinner. All interviewer join the dinner, so I sat on the same table with my interviewer. It is a good chance to know the personality of your interviewer and other candidates.