2 cycles ago our DS interviewed at one of the two large universities for our state. It was over an hour, it was extensive, detailed and he said, the hardest of any interview he had. The interviewer was a USNA alumnus (certificate on the wall, and a ring) and was very intense. At one point, he looked at the list of colleges and noted sternly that the school where the interview was being held wasn't on the list. DS thought it was a total loss at that point. He answered honestly that he didn't want to attend that particular college and why (too close to mom and dad, lol).
When the interview was over, the alumnus cracked a smile, and said, "don't stress about not listing this school on the list, it wouldn't have been my top 5 either". They then chatted about USNA for a bit and shook hands. Scary, stern demeanor was gone post-interview.
I would say, just like with MOC interview, the candidate should be familiar with the different jobs in that particular service, be able to give examples of specific impacts they've had on a club or team. Speak to a challenge you have faced and overcome, be able to articulate how you can be a positive contribution to the community you are seeking to join.