I’ve mentioned before that I have no formal training in writing, and like most things in life, I’m just winging it. For a kid who had to have everything planned out to the nth degree, and hated any deviation from the usual, I’ve grown to enjoy the process of starting a job and not quite knowing where it’s going. I find that, if I waited until I had everything planned out perfectly, I’d never start the job, and it’s better to begin with a very basic plan, gather some data, and adjust my plans as I go along. It took me nearly thirty years to learn how to do this, and it’s been relatively successful, aside from occasionally driving my DH up the wall.
The above is not quite a character arc, but it’s indicative of one thing absolutely necessary for a character arc: change. Very few people want to read a book with completely stagnant characters.
The necessity of change and character growth is one of the best pieces of writing related advice I’ve gotten so far. Sometimes these changes are closely entwined with the plot. Romance is one of the best examples of this, and one that I have some experience with. The basic romance plot is as follows: two people meet, aren’t sure they like each other, and go through some experiences that show- to the characters and the audience- that they can’t live without each other. Their experiences, which make up a large portion of the plot, change the characters, by taking them from two single people to a couple, if nothing else.
So it’s very easy to write changing characters in a romance; if the characters stay the same, it’s not really a romance. In other genres, the plot can be more separate from the characters’ arcs, and the writer may have to consciously add changes to the character’s personality or motivations. This isn’t always easy; too much change and too little explanation, and the reader will start to wonder if your character has multiple personality disorder.
It’s simplistic to say that a character has to go from point A to point B. That implies that a character arc is a single, discrete jump from the naïve little waif the readers met at the beginning of the book, to the hardened warrior who kicks butt in the last chapter. Instead, you, the writer, should draw out the character’s journey, taking them from point A to point Z over the course of the books, with stops at many if not all the letters in between.
Subtlety is key, here. Ironic that I’m the one telling you this; I’m not a subtle person in real life. Quiet, yes; subtle, no. But writing is not the same as reality. Even in a non-subtle genre, where the action jumps up and bites the reader from the get-go, characters should be drawn more quietly. Even if they have big personalities; giving them a slow journey provides interest for the readers who are looking for it. And even readers of action-based genres usually prefer to be hit over the head with explosions and battles, not the sudden revelation that Sergeant James Single, confirmed bachelor, is giving up his army career to marry a nice girl from the suburbs and work in an office. That kind of character arc is possible, but it makes sense to have it take place throughout at least one book and more likely an entire series.
The events that change a character don’t have to be subtle. Blowing up entire planets can be perfectly realistic, if it’s appropriate for your genre (I might not do that in my next regency romance, but, space opera or mil-sf? Sure). But your character’s reaction to it shouldn’t be a complete about-face, turning sweet little Susie Q from next door into Colonel Susan Quentin of the United States Space Force in one or two pages. At least throw in the literary equivalent of a training montage; show little Susie working hard to get to a position where she can go after the aliens that blew up her neighborhood.
Now, if Susie Q is a minor character, you can get away with less subtlety. You, the writer, don’t usually have the time or space to minutely detail every little change to every character. Walk-on characters don’t need to have an arc at all. Minor characters should have a quick explanation of their motivations threaded into the story, but too much of that will exhaust and confuse the reader. As always, YMMV and you’re more likely to succeed if you use what’s appropriate to your genre.
In short, character arcs are useful and nearly necessary in a novel length story. A character’s personality and motivations should be slowly revealed to the reader, and the main characters should change, somehow, over the course of the book. Slower, more subtle changes are usually best, because they’re more realistic (which is not the same as reality), but the events that trigger them don’t have to be slow or subtle. I’m not sure if I’d go as far as my DH, who blows up the scene or has an alien burst through the wall when he can’t think of what to write. Then again, he’s sold more books than I have. So, who knows? Maybe I should add some explosions into my Christmas regency. The characters could hardly stay the same after something like that.