Finish the first draft of you novel. Avoid thoroughly editing or rewriting right away. Instead, give your completed manuscript a single read-through for any glaring errors. Set the manuscript aside and don't look at it for about a month or two, so you can return to it with fresh eyes.
Reread the entire manuscript after a month or two passes. Make any alterations you feel are necessary. Let a friend, colleague or any unbiased, trusted outside source review your work. Ask the person to comment on how the novel succeeds and where improvements could be made. Compile the critiques of multiple sources and use your best judgment on what changes you need to make.
Begin rewriting. Some sections of the manuscript may need only one or two sentences rewritten. Fine-tune your story in your rewrite while making sure any facts, historical or otherwise, are correct. Ensure the authenticity of your story by performing research or hiring an expert to fact-check for you.
Edit the manuscript again. Inspect spelling, word use, punctuation, syntax and grammatical errors. Examine the text closely, perfecting the mechanics of the writing itself instead of the story.
Repeat Steps 2, 3 and 4 until you are confident you have reached your final draft. Proofread your manuscript, narrowing your scope even more for typographical errors and any other small flaws. Make sure your final draft is error free before submitting.