Start coaching youth leagues - usually they have volunteer positions. Or if you know a Dad that does it that you can get on board with, do it.
Read a lot of theory books by coaches that are out there, but don't limit it to a certain sports. Psychology of sport and athletes is a big deal.
In HS, focus a lot of your english classes on sports writing, so you can be involved in your hopes as much as possible.
At
ISU there is a coaching minor I believe, and then do sports management with some combination of philosophy and psychology classes. There are several that focus on handling athletes of all ages.
Then in college, make sure you're doing all you can to be a team manager for which ever sport you're wanting to get into, being around the team as much as possible. Keep pushing, make friends with the coaches.
Next you'll want to get a GA job with a team; always good to keep the contacts of coaches you've worked with, because they could be anywhere, so you could have lots of options.
BEST OF LUCK!
