I started the whole process september 6th, I had my written in and processing by october, was selected in december, physical taken and npq february, applied for waivers in repeating cycles till I got a star to reject it, then finally told to go away april 12th. All was in my Senior year of HS.
As early as you can, is the bottom line. I had skin cancer the year before, the reason for the temporary npq, but the moral is hoops after more hoops, be prepared to jump through them. The quicker and more complete you can make your package, the better.
Now back in the same damn boat applying for OCS, oh well. Good luck with your app, and better luck figuring out what schools you want. Took me 2 weeks to get my head straight on it.