Great stuff here. I just want to add to the good timeline that TWOBOYS posted above pertaining to HA D3 schools with very low admit rates. (The school in the over-recruiting thread is a different kind of beast, IMO. If a kid can't get into a D3 school with a 65% admit rate without help, then maybe playing baseball at a D3 is not the best choice.)
Coach asks player for grades and scores and what he's taking next year.
Player provides same.
At that point, either coach will a) invite kid for campus visit or b) vanish into the ether. (note that sometimes they reappear later on)
If a), the kid goes to campus, and if coach wants him, he says something like "I'm offering you a spot on my team. If you apply ED, admissions says you will be admitted, so long as you don't flunk anything or get arrested etc."
Kid says, okay, I accept. This is all verbal at this point, but if you've asked the right questions (stuff like, when is the last time admissions didn't accept a kid who had been promised admission) and asked knowledgeable parents and coaches about the program, you should feel good about the process and your kid's next four years.
But if your family is like ours, you're not done quite yet. Now you have to ask for a financial pre-read, because the last thing you want to do is tell the kid you can't afford to send him to college when your FA packet arrives in April with an award $10 or $20 thousand less than you were expecting. Coach gets you in touch with the financial aid office and you fill out a bunch of paperwork listing every dollar you have ever earned or spent -- get used to it cause you'll be doing it again in a couple months for real, and then again every year after that.
When that comes back, if it looks good, then you can relax a bit and enjoy your son's senior season.
Good luck!