Have yourself a merry little quilly
"What if all you have is a plot? This is where I am going to deviate from practically anyone you have ever heard from, and tell you this: try writing fanfiction.
For those of you who don’t know what fanfiction is, it’s pretty simple, and I would bet that you have vaguely thought about doing something like it without ever realizing it. It goes like this: you see a movie or read a book or even play a game, something you really love, but when you’re done the first thing that pops into your head is “But what if they had done—-” or “And then what happened?” or “Gee if there had been a character like this—-“
Fanfiction is taking an existing world, and possibly even some of the characters, and writing your own stories in it. And it is a lot less intimidating than making everything else up for yourself (especially when you’re talking about fantasy, science fiction, or horror). Now I am not advocating that you do this with the idea of selling the thing, because that’s called plagiarism and it’s illegal. And there are writers and publishing companies that don’t allow fanfiction to be published in any form, even on the web, so you have to be very careful about that.
But for purposes of practice? It’s fun, it’s going to give you a giant kick-start, and you would be surprised at how many professionals started out that way (and still do it!). Well just as an example, go have a look at all the Star Trek, Star Wars, and game-based books there are out there. If you reduce things to principles, most of those are fanfiction—-fanfiction commissioned by and given the blessing of the publisher, and produced by professionals, yes, but still fanfiction.
And there are those of us professionals that still write fanfiction for fun (although I doubt there are very few who will be as up-front about it as I am). Sometimes it’s because someone else’s creation got us by the throat and our storytelling demon won’t let us go until we get our version down on paper or in pixels. Sometimes it’s because it’s not the genre we make our bread and butter at. (…)
Now get out there and conquer that blank page!"