Getting a publisher is always the best, someone to help you edit the book properly if nothing else.
I was lucky enough to find excellent editors at the Writer's Exchange.
If you do not wish to get help, or you want to try it alone - here's
10 Steps to Self- Publishing
Edit your hard earned work. Pass it around friends and family to read. Make sure they have a red pen to mark spelling mistakes etc.
Edit your book. Yeah, I know that step is down twice but most books really need it. (Mine still needs it)
Save your novel in a variety of formats. Word, rtf and pdf are common downloadable files for reading. Openoffice can save in all three, and it is free to download www.openoffice.org.
Microsoft Reader is another common format and the compiler is a free add-in for word that you can download.
Get yourself a website. You can buy a domain name and hosting quite cheaply. The domain name makes it easier to remember, and lets you register with search engines with a greater chance of success.
There is nothing wrong though. with getting a free page from www.geocities.com or somewhere similar. They have editors that mean you do not need any html skills to set up a site, just pick one of their templates and type it in.Set up a page in your website where you can send people once they have paid to download the book. It can be as simple as uploading the book in each of the formats and sending the link www.mypage.com/book.doc.
Set up some payment methods, say direct debit into your bank account (many people can now do this online, ask your bank how. It should cost you nothing but your normal bank fees.)
Or try a paypal account www.paypal.com. That is free to set up and charges you only in certain circumstances. You can get credit card etc as well, but that tends to start costing real money.Set yourself up an email group for discussion of your book. This lists you in more search engines (for example, it's the easiest way to get into google) and it might just give you some great ideas. I recommend yahoo groups http://groups.yahoo.com/.
Add your book to ebay. It costs about 33c a time. www.ebay.com.au
Tell everyone about your site. Friends, family, strangers in the street, everyone. Make it easy for the word to spread by writing an article for the local paper, 'Local author publishes book for 50c.
Register your website on every search engine, web ring, news group, email group etc you can find. Spend 10 minutes a day trying to find your book on the internet. Think of all the ways you would look if you didn't know the name or author. Then work out a way to make sure others can find you when they do the same thing. Most websites will let you suggest a site or URL for free, but you have to wait. It won't happen overnight, but it won't happen at all if you don't start. Give it a try!