There are not many rules of writing I actually follow. My motto is Learn the rules so, when you break them, you do it on purpose not through stupidity.
There is one writing rule, however, I never break.
"And what rule would that be?" you ask.
It is, "Don't submit your story as soon as you finish it." Put your manuscript aside for a few days (or weeks) after you've finished it. When you go back to it, you'll be reading with fresh eyes. You'll see the typos, the bad grammar, but most of all you'll see the character inconsistencies in the story/character arc. This is when my rewriting really starts.
At the beginning of the story my main character is presented with a problem to overcome. She doesn't know if she can overcome it. She tries and fails. She tries again, but it seems insurmountable. She tries again and succeeds. By the end of the story she has to have changed so the success is believable. Everything that happens in the story has to contribute to that believable success.
If you're interested in learning more about the story/character arc and how to use it in your stories, Carrie Ryan blogged at Magical Words on story arcs and how she uses them in her stories. Let me know if it helps your story writing.