Still working on publishing myself. It's a very difficult process, one I'm working on myself. Pretty much all the advice here is good, but the real trick is to keep trudging on. I've sent a bunch of queries to agents, and only a couple come back. Most never respond. Don't be discouraged. Of course, the best way is to network. Saying in a query letter that so-and-so recommended the addressed agent helps.

Registering the copyright to your manuscript is $35 (with the Library of Congress). Liz has great points and that would be the order I would recommend. What I did (and am going to do) is self-publish the weaker material. In other words, the stories that might be too long/short for a traditional publisher to pick up. I am currently querying agents for two of my novels (expect a lot of rejection and stay positive). If I get an agent, then all new material would be channeled through them. If you want to self-publish (and that is just as legitimate - people have made it their career) then I would recommend using three different outlets. Kindle and Smashwords for ebooks (Smashwords' Premium Catalog goes out to iTunes/iBooks and Kobo, Barnes & Noble, Diesel, Sony, and a library system) and Createspace (owned by Amazon) for traditional printed material. Createspace is completely free except for the proofs (and you don't have to order a hard copy proof). They print on-demand so you don't have upfront costs. With extended distribution (I think it's $25), you'll be able to get the printed book in library systems and Barnes & Noble. Amazon distribution is free. Smashwords and Createspace offer ISBN's for free as well.

I can't stress how important it is to proof your work. If you work on a computer, print it out or stick it on a digital reader and go through it thoroughly. Also, have others assist in editing (fresh eyes from people you trust). You don't need to have a finished manuscript to register it with the copyright office. The most important thing is for your idea to be protected. You can actually preregister it before registering (this is where it can get expensive as it's $115) which will protect you (and the concept) in the interim although you will be required to register the copyright when finished. You can also upload an amended copyright claim with the added material.

Work, work, work, work some more.

Keep writing, because the more you write the better you'll get. If you have writing credits from submitting to lit mags or anthologies, you raise your chances of getting published. Learn how to write good query letters. Send query letters to every literary agent who accepts the genre of your novel. Wallpaper your bedroom with the rejection letters. Keep submitting query letters....

Be aware that sometimes literary agents reject a piece, not because the quality is bad, but because of the current market, or because there is no real target audience to sell it to.

Sometimes, if they have the time and are especially nice, agents will send critiques and edits. Don't be offended if you don't agree with them, and carefully consider whether they might actually enhance your piece.

Writer's Digest is your Bible.

I started a whole thread on publishing here that might be useful to you: [link]

I've had a few books published so I'd be glad to help you out with at least my publishing approach. Be aware, however, that the industry is always changing, so you as a writer also need to change different ways to approach publishing as the industry makes its changes.

Before sending out a manuscript, I would personally try to build some smaller credentials first. Get some smaller works published, enter some contests and get a few ribbons or publications through them. A lot of publishers want to know your credentials and where you have previously been published before. You want at least a few places under your belt so you can give it to them. There are some publishers in the business that I know who won't even look at a writer if they haven't had anything previously published. So, start small and work your way up!

If you can attend any writers' conferences, that's also another great thing to put in your credentials. Not only for an extra point at impressing publishers, but also for meeting people in the industry. Authors, agents, editors, publishers, etc. will be there, and you'll have the opportunity to meet with them. Sometimes, you can even pitch your ideas to them there. I know an author who actually went to a writers' conference and was talking about a future book idea he had and never started and was signed! It was his first novel, not even started yet, and he was picked up by a company. I'd say that's super rare and almost never going to happen again, but behold, it did! (He actually was given a $50,000 contract the next month by the company. How awesome is that?) Even if you can't get to conferences, at least build your contacts with agents/authors/editors/publishers. You can do so online or just finding local authors in the area to talk. I'm in a group of local authors who have a book show every summer and talk to the community about publishing and if they have any questions. It's rather helpful both for us as writers getting more exposure and experience through each other, as for those wanting to publish. Build your contacts!

The next thing you may want to go is register your manuscript at the Library of Congress's copyright office and get your certificate for it. It's the safe way to go for some writers. It doesn't happen often, but I know an author at my publisher's firm who actually had gotten her manuscript stolen by an artist that was working on the art for it (it was a children's book) and had it published under her name instead. Some editors have also been known to "steal" work. Like I said, it's not common, but if you want to protect yourself just in case, there's always that option. (I only did that with my first novel, since it can get quite pricey).

After you've gotten your manuscript all tightened up and edited to the best possible shape it can be, it's time to start querying to agents. A lot of publishers will only take work that have agents representing it, so be aware of that. It's best to start out by trying to get an agent rather than jumping into the deep end looking for publishers. There are specific guidelines for querying to agents, which can be found online in various places as well as in books which help writers on it. The Writers' Digest has one in particular that I found most helpful, giving examples of good query letters and bad query letters. This was what I modeled mine after. Like publishers, agents have their own specific genres, however. Be sure to do your homework and look up as much as you can about the agent you want to query to so you know exactly what they want of you (all agents want different things). That would be your first step in the publishing process.

Now, if you're ever so lucky to get an agent (they are often difficult to get at first: prepare for rejection), here comes more editing. Your agent often will clean up your manuscript and have you do revisions before it's time to send out to publishers. But, once you're done with that, it's time to relax for a little bit (aside from the new query/pitch letters). You may begin sending your manuscript to publishers! Your agent will be doing this, as well, don't forget. More often than not, it is at this point that you'll get your publishing deal.

But, now comes more editing! Your new publishers will have an editing team working with you to make sure that your book is as good as it can be for publication. You'll also be working with the marketing team who will be planning ways to promote your book for you. Here's usually where you get a website for your book, etc. Your agent will also be looking for places for you to have book signings/premieres during this time. Prepare to have your calendar opened! (I had so many book signings the first month my book came out). The next year or so is going to be busy, but it will be worth it in the end!

It usually takes about 1.5 - 2 years for a book to come out after it's been accepted, but it's worth all the work in the end. Of course, you don't stop there. Book signings will usually be set up for you for a while and you'll get to do some small shows here and there (especially locally). Local interviews often happen, as well (another one of mine just came out last week for one of the local papers), so you will be busy-- especially if you're writing more books.

Publishing is a long, hard process, but it's worth it in the end. Do remember that you really can't live off the money you make on your books (not unless you get lucky and make it big in the industry), but it's something to be proud of at the end of the day.

Best of luck to you!

Getting a book published is easy; getting it published well is difficult.