by Gary Smailes


As an editor, I’ve edited hundreds of books. One thing that you quickly notice is that there are certain mistakes that you see repeated time and again. This article contains the five most common grammar and punctuation mistakes I come across on a daily basis. My hope is that by sharing some of these with you, you’ll be in a better position to avoid stepping on these literary mines.


Double Quotation Marks vs. Single Quotation Marks
This one is particularly important to me, because as an editor, it’s a mistake that I see very frequently, and it is one that is very time consuming to fix, which is ironic considering how easy it is to avoid.

  • In American English, the only time that it is acceptable to use single quotation marks in your writing is if you have a quote within a quote (and even then, the author still doesn’t recommend using them).
  • In British English, and seemingly most other countries around the world, the rules on single quotation marks vary far more widely. They are frequently used for dialogue and quotes within quotes.
    If you are an international author trying to market your work to an American audience, please keep this in mind, as you will be saving your editor from a massive headache (and yourself from having to pay for more extensive proofreading) in the long run.


Oxford Comma – To Use It or Not to Use It?
This one isn’t really a rule, per se, so much as it is a discussion point. It’s the “Who shot first, Han vs. Greedo?” of the English world, and depending on who you ask, you’re going to get different answers.

The Oxford comma is the comma that goes after the second item on a list (lions, tigers, bears). Some editors say that you must use it, while others don’t think it’s necessary at all, and more than likely, this great grammar debate will never be solved. While the author personally thinks that writers should use it, ultimately, that choice rests with the author.


They’re, Their, and There
This one is the scorn of high school English teachers everywhere, mainly because they know full well that despite their best efforts to correct it, most people are going to continue making this error until such a time that only the trees, roaches, and Twinkies are left standing. Let’s see if we can break this down simply, because once you see it mapped out visually, this is actually a very simple concept to grasp.

  • “They’re” is a contraction meaning “they are.” Use this one when you want to refer to a group of people, not a place or a thing.
  • “Their” is used to refer to the ownership of something (i.e. an object) and is only used to describe a single person, not a large group.
  • “There” is used to refer to the location of something. It’s never used to describe people or possessions, just the position of an object.
    So all you have to remember is one of them is for groups, one of them is a single person, and one of them is for places.


Difference between A and An
Despite how commonly this particular typo occurs, this is probably the simplest rule that we’ll cover. Once someone points out how to use these two articles correctly to you, it’s unlikely that you’ll repeatedly make the error again.

  • Use “a” anytime the word after it in a sentence begins with a consonant (that’s any letter that’s not a vowel.) For example, you wouldn’t say “an dog,” you would say “a dog.”
  • Inversely, you’ll want to use “an” any time it is before a word in a sentence that begins with a vowel. You’ll never eat “a apple,” but you can surely eat “an apple.”

Just remember that one of these goes with vowels and the other one goes with consonants and you’ll never make that mistake again. Also, an easy way to figure this one out is to immediately “look” at your sentence after you write it. It something seems “off” to you about it, you have probably used the wrong modifier.


Affect vs. Effect
This one is by far the most confusing and though we would never officially cop to it, a lot of literary professionals (writers and editors) will still make this mistake on a semi-regular basis.

“Affect” is used when trying to describe (as it’s a verb) an emotion or an influence on something’s physical state – how somebody is feeling about something. It is always associated with a mood or a physical change in the properties of something.

“Effect,” on the other hand, is a noun, and is used to indicate the end result of an event. It has nothing to do with emotions or feelings and more to do with the concrete facts you can observe about someone or something.

Basically, you can’t see someone’s “affect,” but you can see the “effect” of something they have done afterwards. Affect is the emotion that causes something to happen, while the effect is the aftermath of the event.

There are a lot of other errors that we could cover here, but these five are some of the most common that we give clients feedback about. My sincere hope is that by bringing some of these issues to the forefront, writers will be more aware of what kinds of mistakes we (as editors) are looking for and how to avoid them.




Guest post contributed by Gary Smailes. Gary has a wide experience of the publishing industry and, over the years, has worked as a freelance writer, historian and researcher. He has more than twenty books in print by is represented by agent Andrew Lownie. He’s also the founder of BubbleCow.