All of my tips seem to focus on what not to do. Sorry! I'm a negative person, what can I say? Here are five more things some people might find helpful:
11. Not enough white space:
I'm not kidding. Another way to say this--too many freakin' words! But really, people like a certain beat to their reading, a certain balance of dialogue/narrative. You can tell if you have the mix right by looking at the white space. This is also why it's tough to have scenes with a single character. Dialogue helps with momentum and adds white space. Try not to leave your character alone too often or too long.
12. Backstory overshadows current story
13. Backstory is more interesting than current story
14. Backstory is the story
15. One of my biggest pet peeves that some might disagree with: Don't make the entire story a flashback. Tell the story that's happening now, not the story that took place twenty years ago. I want NOW! And if you want to write about something that took place 20 years ago, write as if it's happening now. Nothing makes me lose interest faster than something that's not happening now. I realize there are some wonderful exceptions to this, but immediacy is more likely to engage the reader.