Have you ever read (or written) a book and felt like the characters were flat? Like everything about them was superficial or uninteresting? Like they lacked depth and complexity? Yeah, me too. Developing compelling characters isn't easy, but I've composed a few questions for you to check off as you create some of your own.
What is their name and why?
I know this seems like an easy one at first glance, it never hurts to give it a second look. I'm not talking about the actual meaning of their name (although you can explore this if you want to), but the time which their name was most popular. You want it to be historically accurate.
For example, you can deduct with confidence that because my name is Alyssa, I was probably born in the 1980s, 1990s, or 2000s. That's when the name was most popular, thanks to this icon.
Next, think about your character's name and describe what it says not only about the time period they were born in, but what it says about their parents. Why did they choose this name? Was it a popular name? More obscure? A family name? Has it been abbreviated to a nickname?
Where do they live? Where did they grow up?
This is a nice touch even if the reader is not familiar with whatever town your character is from. They may have an idea about the region (north, south, etc.) and the culture they grew up in. When choosing a hometown for your character, think about how it affects their worldview, their accent, their dialect, and even their disposition.
What's their relationship with their parents?
Back to the parents. Everything goes back to the parents, even if you're writing Adult fiction. We all know this innately. Don't feel like you have to write a tragic backstory about your characters' parents. Even the best parents mess us up. We learn everything from them at a young age, good and bad. It takes us years to shake the bad habits. Sometimes we don't.
What is their place in the family dynamic?
Mom and Dad are only the first layers. Their siblings matter, too. Not just their personalities, but the number of siblings they have, their spot in the pecking order, and their role in the family. Are they the middle child who gets the least amount of attention? Are they the funny but spoiled youngest kid? The overly responsible but bossy oldest kid? Are they an only child? Do they have half or step-siblings?
This is not to say the youngest kid can't be responsible or the oldest kid can't be funny. You can change it up and subvert expectations. At the very least, think about whether or not they've had to share a room with a sibling. If they haven't, maybe this affects their adulthood in that they have a difficult time sharing space with their roommates or spouse. They're used to having things how they want it, on their terms.
That's a bit of a tangent, but see how those little things matter?! Imagine Kim or Kourtney Kardashian growing up an only child. Um, no.
Who or what do they love most?
It could be a person, place, or thing. It's what their mind defaults to when they're daydreaming. It's what they're most scared of losing. A line from a Mumford and Son's song sums it up best: "Where you invest your love, you invest your life." In other words, it's what they spend most of their time doing. It's something they would go to the end of the earth to protect.
And it could be something good or bad. The most compelling stories test the character's willingness to keep this thing they love intact, no matter the cost. Their willingness to sacrifice tells readers about their integrity and whether or not they should be pursuing this love.
Sometimes the lines blur. Is it ethical, for example, for a man to steal to provide for his starving family? That's what makes the story interesting. Sometimes their actions are obviously unethical. They lie and cheat for self-gain. They are motivated by the fear of losing what they love.
What makes them angry?
Speaking of fear, anger also stems from love. The angrier we get while defending that which we love most (such as political opinions, our actions, or other people), the more we love it.
I'll use an example from my own books. The main character is very vain. She banks on her looks to get her everything she wants, and it usually works. When the boy she likes doesn't pay her enough attention, it makes her angry--as though there is something wrong with him for not being interested in her. It obliterates her confidence and exposes her insecurities.
In my second book, the main character loves her individuality. When her cousin comments that a stranger at the gas station looks like her, the protagonist loses it because her whole identity is built on being unique and significant. If she's like anyone else, her core identity comes undone.
What do they want? What happens if they don't get it?
This innately will be connected to what they want, what they're afraid of, and what makes them angry. All you have to introduce now are the stakes--the consequences of them not getting what they want. If you are writing a more literary or character-driven novel, it will probably be an attack on their identity. Getting what they want will cement what they already think about themself and what they think is true.
It's all the more compelling if they're pursuing the wrong thing--if what they're chasing delivers an empty promise. At one point in the novel, they must make a heart-wrenching choice between what they think they need and what they actually need.
Of course, these aren't the only things that make characters compelling. There are different ways to construct characters and an endless number of questions you could answer about them. Hopefully, these provide a good starting point!