I'll third the idea of reading more, and as large a variety as possible.
I'm no writer, at least not yet.... but thanks to spending a childhood doing some pretty strange things, like reading an entire set of encyclopedia, and dictionaries, just for amusement, I can wrangle the English language fairly well. ( Even for that, I do still keep the dictionary/thesaurus page open while I write, spellcheck not always being up to par. )
Couple that with having read enough other books to fill a large room, I have an easier time than most in figuring out how to make what I put down on paper at least interesting, if not always technically correct.
And no, I don't have any formal education in writing, past the basics you get in grade school, even though I did attend college.
O.H.