So you make full use of your word processors spell check and grammar check features. And you read and reread as you look for errors and tweak your story. Now it's ready. Or is it? I had done all of the above plus critique partners and friends had read it, but there was that niggling feeling that I should do more.
My solution, I used a professional proofreader. Now I was lucky and I have a friend who did this for a living for many years and she agreed to go over my manuscript for me. But even if I hadn't had that good fortune, I would have hired someone. Proofreaders are out there for hire and they are worth the cost.
I sent my manuscript off to my friend, and very shortly, I got a file back with all kinds of little red squiggles on it. I expected errors, but had no idea how many were really there. Most of them were things I knew were wrong the minute I saw them; I had just missed them. Some of the errors were changes in punctuation usage over the years since I took grammar in college more years ago that you want to know, and a very few were things I didn't know. My friend had given me lots of work to do on the manuscript.
So I pulled up my document and I started reading through it again. I made sure I corrected the errors she had indicated, but I also took this opportunity for one more read through of the story. I tweaked a sentence here and a paragraph there. It took a lot longer than I expected, but it was also rewarding as I knew that my book would be the better for it.
It's now ready or at least as ready as I can make it with the help of a professional. And I'm now ready for the next step. I'll be contacting Create Space soon to work out the details of my contract with them. I'm expecting the book to be available by early fall.