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 only appeal to a handful of niche readers, 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 run a business related to the subject. Independent ebook publishing might also work if you just want to leave a permanent, lasting record of your life or your family tree for your loved ones, rather than having to print out a lot of copies.
Also 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, Amazon, Ingram Spark, or Lightning Source doesn't guarantee publishing success, but it does allow you to retain control of your copyright, your text, your cover and your royalties.
Having said that, be aware that most self-published authors sell a handful of books to family and friends, fail to get bookstore 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 and editor's job)!
Still, self-publishing can be done properly. 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 bookstores and having little publicity or promotion. Visit Writer Beware to check the credentials of 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 POD publishing or ebook indie publishing can be stepping stones to publishing success, and some indie-published titles do exceptionally well. Many have even been picked up by traditional publishers.