Writing your book is only part of what has to be done. Of course you want to write the best book possible, we all know that. Once it's done, you're going to want someone who knows the genre you're writing it in to give it a first edit. Pay someone if necessary. If you really want your book to be accepted for publication, it needs to be as free of flaws as you can make it.
Meanwhile, do you know who your audience for the book is? That's always important because that's who you will primarily be focusing your marketing on.
Have you written an elevator pitch that you can easily roll of your tongue?
What about the book blurb for the back of the book?
Do you have a one page synopsis that you can use for blogs and other places for promotion.
Do you have a website? A blog? Are you on Facebook? You should be if your not already.
Have you figured out your marketing plan? What kinds of things will you do in person? Book signings? Library talks? These need to be set up way ahead of time.
Are you going to make a book video or hire someone to do it? Have you thought about a virtual book tour? If so, are you going to find blogs and schedule it yourself or are you going to hire someone to set it up for you? Have you checked to see what book fairs and festivals are close enough to where you live for you to participate in?
Many publishers want to see this marketing plan right along with your query and synopsis.
Are you watching how either authors are promoting? Write things down that you thing you might like to try.
Is your bio up-to-date? You may need more than one--a short 50 words or less, or one with more information.
Once your books are published, you'll want to buy some at author discount for yourself. Some larger publishers have restrictions on authors' selling books, but small publishers encourage the practice. Even if a bookstore orders your books, they might run out and having some in the trunk of your car could be a saving grace.
Hand out bookmarks and/or biz cards with the cover of your book and ordering information to everyone you run into.
That's just a few things to get you started.