First of all, you still have two track seasons left in high school. Train your butt off. Set some nice PRs. Work your butt off over the summer, and come into the year in shape and ready to shred. Email the coaches of your prospective schools some time in the spring to find out the walk on standards. Here is the thing, title 9 is a real hindrance to some D1 schools that may not have a lot of room for male walk ons. Nature of the beast. You may need to be faster than some recruits or scholarship athletes. There's really not much to do on your part besides work hard, get faster, and contact the coaches. You may not have a shot your freshman year. Are you gonna keep working hard? Good luck.
Another piece of advice is that there are so many great schools out there. Not all are D1, but don't be afraid to look around.