First, I have to announce that I haven't been admitted yet till now, so I hope my opinion would not mislead the friends. 

Before my interview, I just prepared the routine questions, such as describe youself, teamwork, leadership, why MBA, why now, why columbia...because I think that's enough, and my interview experience prove that that's really enough. I think the most useful tip in your interview is "be yourself" and show that to your interviewer by your answer(you know, all of your interviewers are very smart and seasoned guys, so please never try to trick them by your boasting or acting ). However, there is nobody in the world know you better than yourself, so take it easy and prepare yourself well.

Good luck!  my friends!