This is what I have learned so far from reading 'Writing the Breakout Novel' by Donald Maass.
1) If you don't like the kind of story you're writing, then why would anyone else? And why are you writing it?
2) Don't write what you know....write what you love.
3) Raise the stakes. Up the conflict. Take the one person your MC really counts on....and kill them.
4) Description is important but only as setting. Think of how a place makes you feel, whether that is comfortable or creeped out, and add that to your story.
For other great writing tips, check out Literary Rambles, every Tuesday.