There’s a lot of advice out there from people who teach and from people who do, but if you really want to be a writer, there’s no getting around it. You’ve got to write.
An article in The Guardian quoted PD James’ “Five Bits of Writing Advice”:
1. Increase your word power. Words are the raw material of our craft. The greater your vocabulary the more effective your writing. We who write in English are fortunate to have the richest and most versatile language in the world. Respect it.
2. Read widely and with discrimination. Bad writing is contagious.
3. Don’t just plan to write—write. It is only by writing, not dreaming about it, that we develop our own style.
4. Write what you need to write, not what is currently popular or what you think will sell.
5. Open your mind to new experiences, particularly to the study of other people. Nothing that happens to a writer—however happy, however tragic—is ever wasted.