Nothing can beat reading for learning how to write better. Reading published authors (RIF Rember "Reading is Fundamental"?) makes us aware of different styles and voices. We begin to see how professional writing is done (of course virtually all of them have good editors).
I just can't stress this enough: you must read more in order to learn how to write better. I believe that the amount of time you spend reading is directly proportional to the level your writing ability increases.
By reading a wide variety of writers one gets to see what the stylistic and even grammatical options are. When you read very imaginative, elegant, and even somewhat quirky writers, you learn that as anything else: you can learn the rules of something, and then develop a kind of mastery in which YOU are now able to use the rules rather than being used by them.
And so on and forth.