Give it one last read-through. Look for the right words in the wrong places (e. g. a typo which turned out to be a correctly spelled word, so spellchecker missed it). Look for sense and ease of understanding. Make sure your plot makes sense.
One of the optional works is On Writing by Stephen King. Being in the writing community, I have heard a lot of things about this book. A lot of people take it as absolute gospel. I am curious to read it for myself already. Regardless of my feelings about his works of art (I am not a fan), I do respect the author, particularly as he really did pull himself up by his own bootstraps.