What a great thread showing how it really is a case of "no one size fits all" for kids who want to play college baseball. From what my 2017 has experienced and from what other kids he knows in SoCal, here is the rank order to best improving your chances to get noticed and play college baseball:
1. Strong HS baseball program in a competitive landscape (i.e. D1 or D2 division in SoCal) where college coaches know most of the players in those games are worth scouting
2. Strong travel ball team that is invited to play in top PG, Under Armour, AZ Classic, etc. tourneys/events where there will be tons of colleges in attendance
3. Outgoing, supportive HS baseball coach with contacts and relationships with coaches in college and who has a good reputation for making the right recommendations
4. Outgoing, supportive travel ball coach who has a network of college coaches and who has a good reputation for making the right recommendations
5. If academically strong, attend a Head First Honor Roll Camp and contact coaches of schools your son is interested in ahead of the camp
6. Sign up for other showcases like Stanford, Show Ball or Top 96 where they name the schools/coaches who will work the camp and then contact the coaches of schools your son is interested in ahead of time.
7. Have your son compile a video and send it in e-mails to coaches of schools he is interested in. Expect that if they are interested, they will respond within a few days and ask for more info (grades, class and game schedules, etc.). Hope to be invited to a prospect camp or visit on campus. No response to e-mail=no interest.
I completely agree with the OP that #2 could be #1 if your son is not playing HS baseball in an area where there is a lot of talent and college coaches come out to watch some games. And even in an area like SoCal that is filled with a ton of baseball talent, it is really only those upper divisions that get the college coaches attention. Of course many of those kids on those teams are then also invited to play for the elite travel ball teams and MLB Scout teams, so they are virtual locks to wind up in D1 with all of the added exposure at the PG national events.
And from our experience, I would highly recommend that anyone who has a son at an average high school program with a coach who does nothing for his kids to promote them to colleges, try to find the best travel ball team you can find as early as you can in HS to make sure your son at least gets a chance to be scouted by the D1s if that is his goal. It is just not going to happen otherwise.