Recently, conversation on a writing board I frequent turned to choosing a publisher. How do you choose a publisher?
Well, you don't choose a publisher. A publisher chooses to publish your manuscript.
If you're self-publishing, you may choose from a number of services.
One fundamental difference is in who holds the rights to publish your book.
If your'e self-publishing, you hold the rights. You can send it to Smashwords, to Lulu, to CreateSpace, or whatever. You probably can (and should) send your work to multiple venues. The thing is, you hold the rights to do that. And you're responsible for everything: editing, cover art, formatting, printing, distribution, the whole ball of wax. It's your job to get your work into the hands of readers.
A publisher will generally ask for exclusive rights for print and/or ebooks, and perhaps take those rights for territories beyond your own country. They should pay you something for those rights, either an advance and/or royalties on sales. They should also should do editing, cover design, formatting, printing (if a print book), and distribution. It's their job to get your book into the hands of readers.
See the difference?
Very simply: If you're paying to get your book formatted, distributed, cover art designed, whatever, you're self-publishing. (Be wary of companies who say they will publish your book at no cost, but instead pile on costs on the back end. "Oh, you want it on the Kindle?" Ker-ching.) A publisher will take care of all of those costs and not charge you a dime. In fact, a fair contract means you should get royalties from sales if not also an advance. There are plenty of small publishers that will do just that. You just need to do your homework, and hope they'll accept your manuscript.)
Which route is right for you? I can't do the math for you. It depends on your specific book, its audience, how much work you're willing to do (or farm out) on your own, and how marketable a commercial publisher might think it would be. Some books do much better with a commercial press. Others are a success when the author does it on their own.
Whichever route you choose, do your research carefully and be sure you understand a contract or agreement before you sign or accept. There are some good resources out there to help. Some are linked on my blog sidebar. P.N. Elrod
suggests you Google the name of the publisher or service and "scam" or "problems." That's a good start. Some people put more thought into buying a toaster than they do selecting publishing services or deciding which houses to submit to.
Your book isn't your baby, but it IS a business proposition. Treat it as such.