Only two things to add:
1) A good, humble attutude- I heard horror stories from my cadet and her roommates about a couple candidates who fell asleep in their classes, acted rudely to cadets, ect.
2) lots of questions- your cadet will be glad to answer any questions you may not have wanted to ask the men/women who would be interviewing you (MALO or nom board). Most of them will be very truthful in their answers, telling you the good and bad sides of everything.