As banal as it might be my advice is to write, write, write, write. And do so as much as possible. I would also say to write for the love of writing and for the love of creating those stories that make your fingertips vibrate and excite you to the point of sleeplessness.
I took almost 17 years off from writing because I became so discouraged with my experience with Northwestern Publishing. I felt like they took away the magic of writing for me when they went out of business. It took a lot out of me. But since I've been writing daily again for the last two years, I feel centered again and much happier. I'm not writing to be published, I'm writing because I have to. It's an addiction and as an addict I can honestly say I'm thrilled to be feeding it again.