Sometimes writing comes easy, sometimes it's like a self-administered appendectomy.
John Scalzi has a post about writing Fiction vs. Non-fiction. He links over to a post by Marissa Lingen that talks about a lot of things in writing fiction (but only briefly).
There's a bunch of things going on in both posts.
But I'll agree with John here that the most important line of Mrissa's post is "If you haven't written a lot of fiction, you probably can't write good fiction right off the bat." This is what's known at the "Million Words of Crap" theory (aka, practice makes perfect - actually, practice makes permanent, critique and improvement give you the continuous improvement process toward perfect). And we only have to scroll down to the sixth response in John's post before we get the inevitable, "But, not for (insert tale of wondrous freak of nature who published their very first novel attempt at the ripe age of 12 for a six-figure advance)" (okay, well, not really in this case, but you know what I mean).
Mrissa also talks about what detail you put into the story to make it work. As a visual artist (that day thing I keep yammering about), I do have a minor in Illustration (which is different than "pretty picture making"). So I have a bit of experience here with what details should be added, what you can shorthand, and what you can leave out that people will fill in automatically (hint, if you want to make people look sinister, draw their teeth with detail). Here is an example about how to imply scale and it doesn't mean throwing in as much detail as you can (grokked from Jay Lake). In fact, it's all about what detail you include, and all the detail you leave out. Writing a scene is very similar. You have to choose which details to show and ignore all the other details that aren't necessary. Those details you show must concrete the image in the readers head and give them the flavor of the place (in a Synethesia kind of way).
And because all of that is a bit heavy, for contrast we offer Jeff VanderMeer's Top 10 Little-Known Freelance Writer Survival Tip and a Basic Instructions - How to Tell a Riveting Story (again, grokked from Jay Lake).