When I was in college studying Music, I took some classes on Music Composition (at the time, I was think I would be a music composer, it didn't work out). Despite my inability to write music at the speed that my teacher expected, I did learn a lot. I remember him telling us that we should really listen to what we were writing and if we didn't like it, figure out why. They "why" part is very important. Just saying you don't like something isn't enough. So, with this mighty question in hand, I started truly listening to music for the first time in my life. I've done it enough times now that I do it unconsciously. Of course, it also helps that I ended up studying Music Theory. Knowing how music is put together has really enriched my listening experience.
Now, you are probably wondering what all that has to do with writing. It's quite simple. Everything. What I learned in that classroom can easily applied to other forms of art. The funny thing is that I didn't make that leap until I read the book How to Write Science Fiction and Fantasy by Orson Scott Card. In it he talked about how he taught his wife how to really read his work so that she could give him feedback. It was at that point that I realized that I could learn more from reading my favorite authors. In a sense, reading to write. The inverse is also true. The more I write the more I can read of my work and figure out what works and what doesn't.
A lot of the books that I've read have mentioned that an aspiring writer should write. It's interesting that none of them explained the purpose. Maybe it hasn't occurred to them. I don't know. What I do know is that the more I write, the more opportunities I have to learn. The more I read, the more I learn to write. There are more "how to" books that I'm planning on reading. I think they can be very helpful. Just about every major author, of every genre, has written one. If you are interested in a genre, look to see if your favorite writer has done a book on their process. Read it. Then figure out what you like and what you don't. Then figure out "why". Same goes for your favorite books. Why are they your favorites? Figure out what parts you like and see how the author does it. I guarantee you'll learn more.
Another thing I learned in college. I don't know if this is true, but it wouldn't surprise me. Mozart learned how to write fugues by rewriting J.S. Bach's Art of Fugue. Mozart wanted to learn fugues, so he studied a master. Note by note, he deconstructed it and learned.