Our son was afraid to practice his answers too much, but knowing how he would be scored helped quite a bit.
In our case, the B&G officer performed 1 interview which will be used for both USNA and NROTC scholarship. I don't know if this is typical, but I suspect not since we were told that this year is the first year information is being shared between the two.
Interview was not formal, but our son was nervous just the same. He was told to dress comfortably, but decided to wear dress slacks, collar shirt and tie just to show respect. B&G officer was in a golf shirt and khakis. As soon as the B&G officer sat down at our kitchen table he said, "you can take that tie off now if you would like to."
After we said our hellos and I offered iced tea/water, I excused myself and took the dog for a long walk. When I returned, they were still inside so dad and I sat on the porch and waited for them to come out. In a few minutes, they did, and we all sat casually on the porch and chatted a little more. B&G spoke kindly of our son and bascially gave him the thumbs up. He told us he'd fill out the appropriate paperwork for both USNA and NROTC. Son is on to the next step, DODMERB today.
What a relief. We truly expected a more stressful interview. No curve-ball questions. The only thing our son said that he was asked unexpectedly was, "if you are not appointed to the USNA and do not receive an ROTC scholarship, what will you do with your future." In our son's case, nothing will change. He would reapply of course, but in the meantime, he'll still attend one of the colleges on his list, still major in aero eng, etc. I suppose the question was to make sure the student is not just looking for a free education when he/she would really rather be studying say art.
The entire interview including chatting on the porch, 1 hour.