Rabbi Dr. Lamm ZT”L had a Bachelors of Science, a PhD in Jewish philosophy, and a very long history of writing well-researched and well-regarded books and articles. He most likely got his start early, and in his college years his schooling required him to be very well written.
So if you want to be a decent writer, read a few books on writing and write a lot of articles. If you want to be a GREAT writer, go to college.