Expect to answer questions on why you want to attend USNA and serve, your activities/leadership skills, and other aspects of your application.
If you haven't read the admissions website and the viewbook...it is a must. Asking questions that can be easily found within either publication or that can be found on a search engine indicates a lack of motivation. Think about "what ifs" --- as in what if you don't get your first major choice, not accepted to USNA, etc. Otherwise, be yourself...answer the question asked honestly and to the best of your ability....answer the question asked (I listed it twice on purpose)...and talk and answer like an adult (don't use slang...look at your BGO in the eye). If you are asked a question and don't know the answer...sometimes it is okay to say "I don't know." If you are pressed to further answer (even if you don't know), then answer to the best of your ability.