Officer interviews vary greatly depending on who is conducting it. The basic items, be on time, dress appropriately, be well groomed, respectful and confident all apply. There was a seperate thread talking about parents involving themselves too much in the application process.... this interview is about YOU, not your parents. By this stage of the game, you should be able (hopefully) to stand on your own two feet.
When interviewing an applicant for a commissioning program, I am trying to determine motivational level to complete the program and answer the question, "would I want this person in my wardroom serving with/for me?"... and what kind of leader would you make? Granted, you aren't going to predict your career based on that interview, but I can probably get a good handle on your attitude, and the depth of thought you have given to becoming a Naval Officer.
I cover some topics, including current events, chains of command (for the enlisted folk, though I wouldn't hesitate to see if a civilian knew who was President, SECDEF, etc). In addition, I might bring up a moral dilema question regarding a first tour JO leadership challenge.
As stated above, others have different criteria. But it all boils down to an evaluation of your character.
Good luck,
John