I'd advise anyone wanting to self publish to first assess their dreams of global publishing domination. Are they realistic?
Self-publishing via Print on Demand or e-publishing might be the way to go if you think your book would appeal to a handful of niche readers, or if you have an accessible market yourself, and if you're a competent computer user and promoter, e.g. you're a public speaker or have a business you can sell the book through. It might also be that all you really want to do is leave a permanent lasting record of your life or your family tree for your loved ones, rather than printing out a lot of copies.
A great choice is to consider Print on Demand or digital publishing, in which you format your work yourself (or with a formatter's help), send it off, and see it on Amazon or the POD associated website and affiliated sellers. Print on Demand publishing or publishing as an eBook using Smashwords, Createspace or Lightning Source doesn't guarantee publishing success, but it does allow you to retain control of your royalties, your text, your cover and your copyright.
Having said that, many self-published authors only to pick up a handful of sales from family and friends, fail to get store representation, and may be sitting alongside product of very dubious quality because POD companies don't vet what they publish (that is the author's job)! Be aware that the books that share your virtual shelves may be riddled with errors.
That's not to say that self-publishing is a mug's game. It can be done properly. And you certainly can make a good living as a mildest author from your indie titles, as plenty of my clients do. But it requires effort, talent, and expenditure, as well as marketing and advertising know-how or the ability to learn it. Indie publishing demands that you generate your own 'buzz' in the form of publicity and social network marketing.
I would urge all authors wanting to self-publish to avoid unscrupulous vanity publishers. Publishing with a vanity publisher often results in your books not being sold in to bookstores, having little publicity or promotion, and selling like, well, cold cakes (rather than the proverbial hot cakes). Check out Preditors and Editors and Writer Beware to get the credential for a company before you request a quote.
There are plenty of great, inexpensive ways to publish your own work in today's publishing climate, whether in print or as an eBook. Many thousands of successful indie authors are great at self-promotion and some have produced chart-topping NY Times and USA Today bestsellers!
Self-publishing is not for everyone, but that's not to say that POD publishing or eBook indie publishing can't be stepping stones to publishing success. Both can be wonderful tools for promotion, and some eBooks and indie published books have done exceptionally well. Many have also later garnered representation by an agent or traditional publisher. However, like everything, it's best to know what you're getting into.