I’ve always loved the phrase “kill your darlings.” It’s a piece of writing advice handed down through the years that encourages authors to cut out parts of their stories—even their favorite parts—when necessary to improve their novels. (For the nerds like me, Slate put together a great history piece about the phrase.) In this case, our darlings are going to be secondary characters.

Secondary characters can be hard to write. Your main character(s) will have change, growth, and momentum throughout the story, but many secondary characters don’t get the same treatment. In fact, they often end up sidelined. It’s a curse of storytelling—you can’t focus on every detail of every character and write a good book at the same time. Readers don’t expect your secondary character isn’t the star of the show, but they will notice if that character is underdeveloped.

So how do you know when your secondary character necessary to your story? We’ll use the STOP method (patent pending) to ferret out useless characters. If you answer “yes” to the questions below, it may be time to kill your darling.

Is your character… STATIC?

If your character doesn’t experience any inner change, you have a static character. There’s nothing wrong with writing someone who is stubborn or unwilling to accept change—those are character traits that can be explored. A true static character ends up being flat and one-dimensional in a way that isn’t interesting to the reader or useful to your story. These characters are the product of too little attention rather than being an intentional choice in the writing.

Is your character… a TROPE?

Stereotypical characters pop up in fiction all the time. If you can subvert those stereotypes or use them to make a point, more power to you. If you’re using a stereotype as a shorthand because you’re not getting creative, kill that darling. A personal pet peeve is the “mean girl rival” trope: the super popular, super pretty, super mean girl who is vying for the same things as the heroine (usually a guy). Yes, there are mean girls out there. But are they all blonde with long red finger nails, three-inch heels, and an evil sneer? No. If you’re going to write a character who falls into a stereotype category, break outside the mold. Give them depth, motivation, and their own personality, even if it’s a mean one.

Is your character… a ONE AND DONE?

First, let me say it is possible to have strong characters who only appear once in the novel. However, if you have a character whose only line is “Hello!” or who interact with your overall story in a meaningful way, they probably aren’t vital. The true test here will be to see how much of an effect this one appearance has on the rest of the novel. If this character causes a ripple, keep them. If they pop in and out of existence without so much as a blip, kill them.

Is your character… a PLOT DEVICE?

Characters should certainly influence your plot, but no character should exist for the sake of plot. A plot device is a quick fix, a workaround, and using a character solely to advance your storyline is—quite frankly—lazy writing. You have to think of your characters as real human beings (or real aliens or animals or monsters) who have hopes and dreams and fears and their own stories. They cannot be picked up and dropped in the middle of a scene because you don’t know what to do next. Find a natural way to move your story forward, with or without that character.

When it comes to writing secondary characters, there is one all-important rule: Make each character count. STOP writing characters who don’t count, and start writing ones who do.