We had to sign a nondisclosure agreement regarding the interview so I don't think you'll get a lot of information on a public forum like this. I think the best answer to your question would be that there's really no good way to prepare for it. Just be your best self. ? Good luck!!!
I wonder how many people they interview in total? I read in a previous post that there are ~350 applicants? That's a huge number of candidates on a waitlist for 35 spots...
Did you guys get an email from the university saying you were "on hold" specifically? I also interviewed on the 17th but have so far only gotten a thank you for interviewing email with a "we'll have a decision soon" type of deal.