What is the main conflict in your story?
What is at stake? What is the source of tension in your story? What drives it forward?
How can you make this conflict central to your story? How can you dramatize and clarify it?

Are your characters suffering enough?
What are your characters made of? Suffering will reveal it.
How can you make readers care about your characters? Make them suffer.

What are your characters’ weaknesses?
Do they have flaws? Are they human or simply disguised wish fulfillment?

How has your main character(s) developed?
How have the events of your story changed and transformed them?

Are you starting and ending at the right place?
Do you “start as close to the end as possible,” like Kurt Vonnegut advises?
Do you immediately introduce the main question or conflict of the story?
Do you end as soon as your story’s main concern or conflict has been resolved?

Is your dialogue effective?
Is it punctuated correctly?
Are you overwriting synonyms for ‘said’?
Does your dialogue ring true when spoken out loud?
Do different characters speak differently? Do you let characters speak for themselves?

Where have you forgotten to ‘show and not tell’?
What are you describing that you could show through characters’ speech or actions?
Where are you being generic or abstract when you could be specific and personal?
Is your narration invisible? Or do you keep reminding readers this is a made up story?

So what?
Why is any word, sentence, paragraph, chapter, plot point, or character in your story?

Have you used minimum means for maximum effect?
What jargon can you dispense with? What big words can you replace with little ones?
Where can you shorten and subdivide your sentences, paragraphs, and chapters?
How can you get to the point quicker? What can you cut while preserving and sharpening the same effect?

Is your language fresh?
Are there clichés in your text? What can you rephrase to be more original or poetic?

Who are your writing heroes?
How does their text compare with yours? What are they doing that is worth imitating?

Who are you writing for?
What is your intended audience? When you write, who do you imagine reading your book?

Download this writers’ checklist and the checklist for readers in in one PDF file.

For extra credit, check out the Turkey City Lexicon, a funny wordlist that distills a lot of great advice on writing fiction (especially science fiction).