Your DS should read every page, link and drop down on the USNA.edu website, ditto elected rep/senator nomination sources. Build out a timeline and action steps. This is his year to get smart on the process. He should also spend a lot of time thinking about "what comes after," the years of service obligation, as well as Plans B, C, etc.
Research NASS and other common summer activities, such as Boys' State.
He should also explore the four other Federal Academies, to rule them in or out.
Scan the "chance me" and "stats" threads on here to see what both successful and unsuccessful candidates present in terms of grades, class standing, test scores, classes, leadership, sports, community.
Read the medical info pages at USNA.edu, so as to be prepared for any surprises in the physical DQ area. There are some conditions for which the candidate has to be off medications for x period of time or not require accommodations.
Above all, let it be his process to execute, with you in a supporting role. The process itself is a test of diligence, perseverance and attention to detail - for a reason.
Visit if you can - take the Visitor Center walking tour and attend the Admissions brief (details on USNA.edu).
(I know he has already done some of this, but this gets asked in various forms, so my stock answer just pops out.)