I posted a few days ago (ok... ok... it was a couple of weeks) about how to succeed in writing and mentioned that you actually have to write.
Afterwards, I realized that, of course, I was merely echoing the great Robert Heinlein in his Heinlein's Rules from his classic essay On the Writing of Speculative Fiction, published in Writing Science Fiction & Fantasy. The master was being less than honest, however, in that much of what he says applies to all fiction, most especially his "rules". The essay is available in Google Books and I recommend reading it. But I'll quote one particularly salient paragraph. He said about his rules:
...they are amazingly hard to follow--which is why there are so few professional writers and so many aspirants, and which is why I am not afraid to give away the racket! But if you follow them, it matters not how you write, you will find some editor, somewhere, sometime, so unwary or so desperate for copy as to buy the worst old dog you or I, or anyone else, can throw at him.
Times have changed a bit with most slush piles about ten feet deep what with word processors and email submissions, but most of that is still true, in that you will sell if you follow his rules and that very few people will.
So I said the first rule: Write.
What's the second? FINISH. A hundred half-written stories aren't going to either improve your writing or get published. But that one is a hard one. Right this second I'm procrastinating on a novel. I'm 35,000 words in and the thing has turned into pure drudgery. But I have to finish it. I WILL finish it. (*gives self kick in the rear*)
Will you finish that piece you've started? Because if you don't... Well, I think Mr. Heinlein said it.