The interview that I was referring to was the interview for the Honors Program. I did that while I did the Scholars/Pre-knob visit back in November.
For the Scholars/Pre-knob visit, the interview was as kpwehope said. They divided us into groups of about 3 students( all of whom had written on the same topic), and put us in a room with a teacher to discuss our essay topic. I don't recall actually having our essays in front of us, but I may be mistaken. The way that it went for me, was that the instructor introduced the topic, let the three of us discuss the topic for a while, and then took the discussion in another direction that made us think outside of the positions that we took in our essays. I was very impressed with the instructor that was with our group; he certainly knew what he was talking about.
There are 18 Citadel Scholars Scholarships, and a number of other full ride scholarships ( I counted about 30 from the website online, but some were specifically for South Carolina Students, or those from particular counties or regions). I heard that a few were given out in December, and that most will be given out after the other scholars competitions (although I don't know exactly how many/when they will be given out). All in all, they will be bringing in a 100 or so students, to compete for the 25-30 scholarships.
It would be wise to schedule the Honors program interview while you are there. I did mine while the cadet that i was shadowing was attending classes. They don't inform you of whether you are admitted to the Honors Program until about April, I believe. But if you get an academic scholarship, then I'd say you're probably in good shape.