So, you're ready to write a book, and you've decided that self-publishing is the way to go. I'm sure there are many ways to do it, but the one I use (and it's very popular) is CreateSpace. (CreateSpace books are moving soon to Kindle Direct Publishing.)
Go to createspace.com and click start a title for free.
Create an account.
Download an interior template (Word doc.) in the size you want your book to be.
Start writing. I use the font garamond or avenir size 11. If you choose a different font, be sure it is compatible with Word.
Do a "brain dump"; don't edit.
Write the easiest chapters first, leaving the introduction and final title for later.
Insert any photos, images, or chapter headings. You may decide to make chapter headings as an image to be inserted so that you can use any font you want.
Keep in mind that even blank spaces in your document have an assigned font and font size. This is important for keeping your spacing lined up correctly.
Now it's time to edit. Read through your document over and over until you can't find anything else you want to change.
Print your document and edit some more. You will find new errors because things look different in print.
Contact people who you would like to endorse your book. If they are willing, send them your manuscript for review. Follow up with them in two weeks and if necessary every two weeks afterwards. The kind of people who you would choose for this are very busy.
You can design your own cover or pay someone else to do it. CreateSpace has cover templates in the size you need all ready for you to download.
Make sure your cover and title are amazing. Don't skimp on this!
Submit your interior and cover files to CreateSpace for review. They will respond by email within 24 hours.
Order a proof copy of your book for editing. Read through it thoroughly and get some grammar wise friends to read through it as well. If spelling, punctuation, and grammar are not strong points for you, you may want to pay a professional editor.
Approve your final version in CreateSpace. You can put it directly on Amazon and into some stores, or you can purchase copies to sell yourself.