Remember the word: Dimension.
Last year, I read a novel, a story about this young girl who leaves her home and goes to study abroad. It was rather soapy and I read it for reasons other than entertainment, but turns out it was a good thing that it crossed my path – I can now use it as an example on what not to do when developing characters.
So, girl leaves her traditional, patriarchal family and goes to Paris where a life of art and passions is supposed to be waiting for her – all innocent, all full of hope, all that jazz. This is clear at the beginning of the book.

On the last page, however, much to my eye-rolling disdain, I found her the same person, and I mean the exact same person she was on page one. Years had passed, she went through love, bad relationships, abuse, disappointment, domestic violence, gaslighting, abortion – so many of the shitty things life can offer… and emerged just as she was before, in the end.
This never happens in real life.
Now, you may think, oh, that’s amazing, she didn’t lose her innocence, her zest for life – BUT! There’s a difference between not losing your zest for life AND remaining the same moron you were when you were 18 years old.

We build the story around our characters and put them through situations that will help them grow as persons, just as it would happen for someone in real life. That’s character development and your character has to be dragged through proverbial mud to grow. At least they do, if you want a good story.
Here’s what you can do: Start thinking about the people you’ve known for a long time – how they were and how they are now. What their behavior is like, what their attitude is like after a particular event in their life, or a certain series of events in their life. You’ll find that it’s an interesting study and you might even find out new things about the people you know, things you hadn’t realized before.
Use that. How have they grown? Surely your neighbor that you’ve known since you were kids is not the same person at age 9 and age 39 after high school, college, marriage, divorce and three kids? Your sibling couldn’t be the same person they were at their prom and now, when they’re running a company? Of course, they will have the same character traits, the same laughter, they’re the same human being. But their behavior? Their perception of the world?
Borrow traits from people.
Borrow fascinating, real characteristics, idiosyncrasies and attitudes. What would a person you admire say in that particular situation? What would the most annoying person you came across this week do? What would that person you hate say? Make your MC feel what you feel for that person, it will come off real.
Always make sure your characters have more than one dimension.
A positive character is not the best at everything. If they speak seven languages, they might have phobias. If they’re the absolute best architect in the world, they have a drinking problem. If they don’t have a bad bone in their body, they’re unconsciously selfish. And if your protagonist starts as a perfect person who has it all, you better make sure they get tripped somewhere in the story. If they start off flawed and insecure, trip them some more.
A villain has several sides apart from true evil.
A protagonist needs to have flaws.
If they don’t, they’re one-dimensional, and that’s a crime against characters, which makes you your writing’s worst enemy.
If they don’t grow, they don’t exist.
tl;dr: Put your characters through hell. Whether it’s lighthearted, romantic comedy hell, or serious hell, it’s up to you and your genre – but make sure they grow.
Jana