ATC Timmy
You'll find most people won't give away too much about the game. If you do a search on Proone, you'll find what you need. Here is a brief run through:
1 Assessment day: Spatial Reasoning, Arithmetic and Psychometric Testing etc all against the clock
2 Interview Day: Technical Interview, HR Interview and the dreaded computer tests (collision prediction and arithmetic)
3 Medical
4 College: Well, you'll find out when you get there!
5 Unit Training: Worry about steps 1 through 3 before even thinking about this one.
All these points have been expanded on numerous times - do the search/legwork yourself, it will pay off in the long run.
CF