You've probably considered the merits of self-publishing your book versus finding a publisher. Regular readers know that I lean in the direction of working with an established publisher. I've done dozens of books that way. But, though some of us cranks hate to admit it, there is a trend toward self-publishing. I don't believe that self-publishing and "author control" will make bad books succeed, but there are some writers who have been wildly successful serving niche markets through self-publishing (mostly with good books). Self-publishing is not an automatic route to success, as much as book printers and pay-to-publish operations may want you to think that. Some good books have failed at self-publishing, too.
Anyway, the current issue of Entrepreneur Magazine has an interesting article titled "How to 'Invent' Your Book." (Thanks to Joe Wikert for posting about this in his blog.) Tamara Monosoff, who wrote the article, has herself written a couple of books and explains in useful and mostly accurate detail how each process--self-publishing and conventional publishing--work, along with the relative benefits and drawbacks.
Monosoff does get one thing wrong. She says, "Very few publishers today accept unsolicited or un-agented manuscripts." This is true for outfits like Doubleday, Simon & Schuster, and Houghton-Mifflin (though some of their subsidiaries accept unsolicited manuscripts), but there are hundreds of publishers who do accept unsolicited manuscripts. And they're not all tiny shops that have poor distribution and pay thousand-dollar advances. It is true that a few editors will talk only with agents, but you can sell your book yourself. Don't take to heart Monosoff's recommendation that you find an agent rather than try to market your work on your own.
If you feel you must have an agent because you fear negotiating and dealing with contracts, pick up a copy of How to Be Your Own Literary Agent, by agent Richard Curtis. Still want an agent? Start shopping, but be aware that you will be holding up the potential publication of your book as you wait for agents to say "No." And most will say "No." Getting an agent is frustrating, time-consuming work. Just to be on the safe side, shop your manuscript(s) to publishers yourself while you're waiting for agents.
Perhaps my perspective is a bit skewed because acquired books for publishers, agented for other writers, and used an agent for only one book out of 42. But it's true that you can sell your own work to a decent publisher, and that self-publishing is not an automatic route to success, for good books or bad.
That aside, do read Ms. Monosoff's article.