If you participated in National Novel Writing month, you just have a few more hours (depending on when you read this) to finish. If you "won," congratulations. When I finish a book, it's a kind of high. All those moments in the middle when it felt like a slog and I was tempted to give up are forgotten, and when I get to the end, I'm convinced it's the best book ever. You may be tempted to send it off to editors or agents or upload it to Amazon right away.
Most editors and agents are winding down their reading for the year, trying to clear out their in-boxes before the holidays, so sending it now probably won't do you much good. And it's probably not ready for publication. Here are some things you might want to do before you try to get it published:
1) Put it aside. Enjoy the holidays. If an idea relating to the book strikes you, write it down, but otherwise don't look at the book until the new year. Giving yourself some distance helps you make better revisions. That's because right now, you're still attached to the emotion of writing it. You remember which parts were difficult, which parts came easily, where you got all the ideas. Remembering all that makes it more difficult to make the right edits. I've often found that when I look at a book again after a break of more than a few weeks, there are things I don't understand about my own plot, or I don't get my own jokes. Distance allows you to come closer to reading it like an editor might.
2) When you get it out, try to read it like a reader would. If you've got the technological capability to put it on an e-reader or tablet, do so, and then just read, not editing, but taking notes if something strikes you. This read is more for plot structure -- when does it drag? Is there something that doesn't make sense? How does it flow? Try to outline the piece and see how it holds together, then figure out what major surgery needs to be done. Are there scenes that need to be cut, added, or replaced to make the plot work? Do scenes need to be rearranged? Do you need to add or cut a subplot? Are there dangling plot threads you need to deal with? Are there any continuity errors that require you to set things up earlier in the book so they'll work at the end?
3) Now you can get down to editing. I generally make at least three passes. The first is the major surgery -- the bulk of the rewriting. That's when I add, cut, or replace scenes and make the plot work. The next pass is to make the words pretty. That's when I make sure the writing is tight, that I'm not repeating words too many times, that the jokes make sense, that all the words that need to be there are there, that I've used the best words for the occasion, that the character voices are unique. The final pass is proofreading, and then I usually read it out loud. That's when I spot awkward sentence structure, missing words that my brain tried to fill in, repetitions, and clunky dialogue. I often change fonts in the document between each phase, which makes it look like a different book. Words are in a different place on the page, which makes you see them differently, and it creates juxtapositions that may show you that you're repeating words within a paragraph or page.
4) Find someone else to read it. This is especially true for a first book. Get someone you trust to give you feedback. You can find critique groups or partners in online writing groups or in writing organizations. Friends and family aren't necessarily a good bet unless they're writers or avid readers who will give you honest feedback. And when you get feedback, accept it graciously. The goal for all of you is to make the book better. You're not helping the book if you get defensive about criticism and treat the person giving feedback like an enemy who's trying to hurt you. The criticism may be wrong, but you may have done something wrong that led the person to make the wrong conclusion. If something's unclear earlier in the book, it may lead readers to make wrong assumptions that affect their reactions to something later. Really mull over and think about the feedback before you accept or reject it.
5) Then you may go through another few rounds of revisions, fixing things that came up in the feedback, then proofreading after you've made those changes.
6) Now you might be ready to submit, though it might be a good idea to let it rest again for a week or so and give it one more read. Meanwhile, you can be researching your options. Don't submit to an agent or publisher without doing your research. Make sure you're dealing with legitimate agents who actually sell books and legitimate publishers that actually put out books. See how they like to receive submissions and work on your query. You may want to customize the query for each person you send it to. If you're thinking about self publishing, do some research into that.
7) Now you can send queries to agents or editors, if you're planning to take that path. If you're going to self-publish, you need to find an editor to hire. You might want to get a developmental editor to work on the story itself, especially if it's a first book, and you definitely need a copyeditor. You'll also need an artist and/or cover designer. Look at the books that are out there and see how yours will fit into the market. Independent publishing is easier than it once was, but you can't just throw something out onto the market and expect it to make money. You need to put some work and money into it.