Congratulations on all of the interview invitees. And if you haven't gotten an invite, just hang tight. The MFA process is about finding a good fit on both sides. If Columbia doesn't think you are a good fit, why would you want to go? Know what I mean?
So I hope I can be helpful.
Most of the Dir/Scr candidates last year were interviewed by
Eric Mendelsohn and
Dan Kleinman. I interviewed with them over Skpe and not in person.
It lasted about 45 mins and what really struck me, and what was different from my other interviews, was the familiarity both of them had with my creative materials (ie my script samples, portfolio film). Eric asked very pointed questions about certain aspects of my film. This makes sense of course, but I was pleasantly surprised that I was able to actually answer specific questions about my work and not general questions about film.
Eric did alot of the talking and Dan asked a few questions. Having known them in a school setting this is actually their personalities and not some "put on" for interview purposes. Eric's analysis of my film actually makes alot of sense; he runs a "Film Club" where he spends an entire day with students breaking down every shot of a film.
By biggest advice is to just be yourself. Don't try to be someone you are not. Be comfortable. Be relaxed. They are looking for a certain type of filmmaker and you are looking for a certain type of school. The only way it will be a good fit, is if both you and the school are open and honest with each other about needs/wants.
Best of luck!