In the olden days, when traditional publishers had a crew of talented editors aboard their ships, a writer had someone to suggest changes and to perform the final proof-reading.
Nowadays, editors are being tossed overboard. If your book is traditionally published, your manuscript should get at least a cursory once-over if not three. However, being published by a big house is not a guarantee that your book will be solid or error-free anymore.
Self-publishing means you must either: be a good editor, know and bribe a good editor, or hire one. Hiring an editor is tricky. Anyone with a fair grasp of English can hang out their shingle as an editor. If you decide to hire one, check their credentials. Ask for references. Do a criminal background check, just kidding, but only slightly. Search for them on the Preditors & Editors website: http://pred-ed.com.
I highly recommend you have several people with some knowledge of craft go over your work. I'm not talking about Cousin Dick or Aunt Sally, unless they are experienced fiction writers or possess a degree in English.
I'm suggesting other writers, preferably those with grammar knowledge and those who have studied the craft of writing. Have them proofread your manuscript for you. Pass out printed or digital copies freely and let them go to town.
Don't worry. They won't steal it.
I guarantee they will catch things you can't. Even if your critique group critiqued your draft, the final product needs to be gone over thoroughly.
If you self-publish, after your file has been uploaded don't hit "publish" yet. Order a proof. Reread it and make changes.
Order a second proof. Reread it and make changes.
Order a third proof and proofread for periods, commas, and typos until you've found every last error you can find. You'll be amazed at what you missed in the first and second proofs. I assure you there will still be one or two errors in the finished product. What you want to avoid is one on every page.
Errors are speed bumps that affect the reader's enjoyment of the ride you are taking them on.
Stringent editing keeps the reader focused on your story instead of your punctuation and word usage.
For more on revision and tips on proofreading pick up a copy of Story Building Blocks III: The Revision Layers available in print and E-book.
What Does An Editor Cost?
Diana Hurwitz is the author of Story Building Blocks: The Four Layers of Conflict, Story Building Blocks II: Crafting Believable Conflict, Story Building Blocks III: The Revision Layers, and the YA adventure series Mythikas Island. Her weekly blog, Game On: Crafting Believable Conflict explores how characters behave and misbehave. Visit DianaHurwitz.com for more information and free writing tools. You can follow her on Facebook and Twitter.