Scour the NROTC and school unit websites, so you don’t ask questions whose answers are readily found.
There are many threads each year here on SAF about nom interviews, SA interviews, ROTC interviews. Go find them.
Have some questions ready to go.
Focus on listening to the entire question and don’t let your brain already be thinking about the answer. Listen to understand first, then to respond. This is invaluable when it’s a two-part question, as in “Tell me why the Navy option is what you are interested in, and then your top 3 Navy warfare communities that would interest you.” You answer the first quickly, because your brain went into “respond” mode, and you completely forget the second half. Or you realize there was something else and have to ask for it to be repeated.
Be prepared to discuss your motivation, interest areas, academic and personal strength areas. “Balancing NROTC requirements and college requirements can be challenging. Are you prepared for that?” “Yes, I am prepared, because I focus on time management and prioritization. I currently juggle 2 AP courses, a varsity sport, volunteer STEM tutor hours, President of the Math Club and work two days a week at Chick Fil A. I know it will be a challenge and hope to learn from more senior midshipmen what has worked for them.”
You can google college interview skills, and wait for helpful posters here.
Think through what you are wearing, so you are confident, and there is nothing to fuss with. Well-groomed and professional. No heavy body fragrance or distracting jewelry.
You can smile! Don’t forget to thank people, including any administrative people with whom you engaged with on your way into the interview.
Practice your handshake. Firm (but not bone-crushing) and professional, same pressure for men and women. If you learned that special handshake for women where it is the light hold of the fingertips, save it for the elder ladies in your family who might have arthritis in their hands.
And - keep n mind ROTC/college is a 4-year waystation to the Real Thing - some years of obligated service as a commissioned officer. Do your legwork on What Comes After.