1. The prose flows naturally.
2. There is an equal balance of humor and seriousness.
3. You actually learn something from it.
4. The characters are believable.
5. The characters go through a significant change of some sort, whether physical or mental.
6. There is some sort of conflict going on; not all goes well.
7. Good descriptions, vivid but appropriate; the best stories are where the audience has a good idea of what's going on and yet they're still free to use their own imagination.
9. Proper spelling and grammar.
10. Appropriate for intended audience.