Like every reader, I’ve come across typos and small continuity errors in novels and short stories, but few created the world-wide uproar as the error found on page 667 of Harry Potter and the Goblet of Fire, the First American edition, July 2000.
Voldemort and Harry’s wands had met in battle and the result was Voldemort’s ghostly victims spewing out in the reverse order that he killed them, that is, his last victim coming out of his wand first. When Harry’s parents appeared, his father came out of the wand before his mother.
My son was seven years old in the summer of 2000. My husband, my son, and I were reading aloud this fourth book in the beloved Harry Potter series and we immediately realized the mistake. Since it was Lily Potter’s love of her son, Harry, which destroyed Voldemort, she should have come out of Voldemort’s wand before Harry’s father. See http://www.hp-lexicon.org/about/exp-wandorder.html for more details about the wand order problem.
What lessons did I learn?
Primarily, I learned that even one of the bestselling authors of all time makes mistakes! (http://en.wikipedia.org/wiki/List_of_best-selling_fiction_authors).
Secondarily, I learned that writers must utilize many proofreading tools to minimize typos and continuity errors.
Here are a few of my favorite proofreading techniques:
One: Read what you’ve written and then read it again. And again. Read it until you can’t find any errors. But don’t submit yet. Your proofing has just begun.

Two: Read it out loud. Hearing your words is like turning on the light in a dim room. Errors shine in the spotlight of the voice. Words should flow off the page. If you stumble as you read your own writing aloud, imagine how it will sound to others.
Three: Record your voice as you read what you’ve written. My favorite way to record my voice is with my I-Pod. Under Extras, I select Voice Memos. I record a piece and listen to it over and over until I catch all the elusive logic and continuity errors.
Four: Ask others to read your work. This is when being a member of a great writing group REALLY pays off. Having three or four or five other people read and discuss your work helps you find everything from simple typos to major plot problems. Yes, you can ask your parent or spouse to read your writing, but can they give you objective feedback? Probably not. For more information on creating a great writing group, go to https://baccaliterary.com/how-to-create-a-writing-group/ 
All of the above works well for small pieces. Short stories or poems. But what about novels? Reading 80,000 words aloud would be exhausting. The answer:
Five: Text to Voice software. Text to Voice software converts the words you’ve written into a natural sounding voice. This is especially helpful when listening to multiple chapters. I use NaturalReaders. A downloadable free sample of NaturalReaders is available at http://www.naturalreaders.com/download.php.
NaturalReader is a Text to Speech software with natural sounding voices. This easy to use software can convert any written text such as MS Word, Webpage, PDF files, and Emails into spoken words. NaturalReader can also convert any written text into audio files such as MP3 or WAV for your CD player or iPod.
Additional proofreading suggestions
from guest contributor
Constance Renfrow,
courtesy of DIYMFA

What to Know Before You Submit Your Novel