I don't know the answer to this but if I were you, I would make a list of Sports Commentators you respect and reach out to them on Twitter to ask questions. Also, find a few locally you like and ask if you can shadow them for their next game to learn more and take notes. Identify yourself as a student for a better chance of response.
Ask your school counselors and Athletic Director if they can arrange some opportunities for you to shadow some sports commentators. Start with the commentators who call the games for all different sports at your own school.