Ensuring consistency is a big part of my work as an editor. As I work through a book I make sure there are no variations in how words are spelled: it should be either while or whilst, never both in the same text. The same with words like among/amongst, towards/toward, and O.K./OK/ok/okay. Numbers below 10 are either written out or not. Or all numbers are written out. Or not. Or only when accompanied by a measurement, e.g. all six competitors were over 6 feet tall.
Chapter titles should all be the same: centered or not, same typeface throughout. Any lists should have the same punctuation each time they appear: a period, semicolon or nothing at the end of each line. Always one or two spaces after a period, never sometimes one and sometimes two (but let’s not get too deep into that discussion).
Editors use a style guide to keep all this consistent, sometimes following an established one, like the Chicago Manual of Style, as well as keeping an individual style guide for each new book to make sure the particularities of that book, or series, are always the same, such as character names and place names. Does the character have blonde hair (or even blond hair)? How many children does the character have, if any, along with their age, size, occupation and so on.
These are all easy to keep track of  and easy enough for an editor to change. It’s part of the job. What’s more difficult to revise is when characters don’t behave consistently. And that can happen very easily.
Avoid a major rewrite
Maybe your hero has always been a good friend but chooses to go watch a movie rather than bail his best buddy out of jail. If the buddy gets out of prison the next day and they argue about the bail before the story continues, then there’s not much of a problem. If the buddy dies in jail and that’s what sends the hero to investigate the death, it could look contrived, a touch too convenient that the hero was at a movie that night.
Such inconsistencies can lead to major revisions, a bigger rewrite than you were hoping for. And it’s better to catch these things before you send your manuscript to an editor—and definitely before submitting it for publication—because a major rewrite is likely to mean at least one more round of copy-editing.
And it’s easier than you might think to introduce character inconsistencies into your writing. You could have had a long break between writing chapters because, well, that’s how life goes. Or it could be that you don’t yet know the characters well enough to know how they’ll react to each specific situation.
There’s not a lot you can do when life gets in the way. You can try to develop good writing habits, write at particular times every day or week, set goals to write for an hour, two hours or 1,000 words at each sitting. But eventually something will happen to get in your way again.
Discover your characters
There are, however, various ways to help you get to know your characters and make sure they react consistently throughout your manuscript. Some authors write letters to themselves from their characters. Others interview their characters as if they’re applying for the job of being in their book. You can write biographies for each character or answer a set list of questions to develop a character profile.
To discover how your characters might behave in certain situations, it can be useful to look at broader aspects life to find out what would be most important to them. This can help you weigh up which direction your characters are most likely to take, what are they most likely to choose when it comes to the crunch.
The idea here is similar to that of my previous article on how to write something that will change your life . Knowing what’s important to you as an author can help give your writing some direction, to guide you through the process.
And your characters can use that kind of help too. In fact, you can use the same exercises for your characters. Another way is to look at the following seven areas of life and determine how they will affect your main characters. You don’t need to go deeply into each if they don’t all apply to your story, but try to work on as many as you can. It’s important to remember that these are not goals, this is not about what your characters want in life but what is important to them.
If you already know your characters’ goals, however, that can help you discover their values, just ask why they want that particular thing. Why does he want to leave his small town? Maybe the city is the only place he can tell the story of the big corporation that’s destroying the land, so he might value nature or protecting livelihoods or the truth. Or all those things. Why does she want to reveal her painful past? Because she values honesty in her relationships.
The seven aspects to look at are: self; family; friends; romance; spirituality; work/study; leisure.
You can begin by arranging each into the order of importance for the character then, for those that are most important, examine them more closely and try to find specific values, areas in life that are important to your character.
Think of each in a broad sense. Spirituality, for example, could be about meditation or nature as well as an established church or religion. Friends can include colleagues or other people the character comes into regular contact with. Family could mean a specific family member or the idea of family. Perhaps family means security for your character, or loyalty. But your character’s value might be respecting boundaries and perhaps not all family members adhere to that.
Work and study might be about a love of learning in general, ambitions or volunteering. Or maybe your character would rather be anywhere else but school, then it could be that she values freedom. If your character’s occupation is thief, it might seem difficult to define a value for that job, but then you can ask why he steals, what does he ultimately use the money for? Supporting family might be an important value in this case. An example of this would be Walter White in the series Breaking Bad. He became a drug dealer to get enough money support his family when he found out he had cancer.
Look at each of the seven aspects and write down three or four core values your main characters have. When they come to a crucial point in the story and you’re not sure which way they’ll jump, remind yourself of their values and that will show you what’s most important to them and what their preferred choice is likely to be.
You could also look at the important moments in your story, those crucial turning points and make sure the characters act according to their values. If they do, then your characters are behaving consistently, which will strengthen your story and help you to avoid major rewrites later.
What values do your characters have, and how do you discover what was important to them?