How do you want people to see your character? This isn’t only about remembering to tell them about hair color and eyes, it’s about personality. It’s also about timing, about when you reveal information.
Early on, you want to paint enough of the picture, to where they can see who you see. However you may want to hold back on certain details, until the proper moment. For example, your character may seem weak and indecisive at home, but two chapters in, the reader sees them confident and in charge at work.
If you do it abruptly, they’ll say wait a minute. If you explain it with a lead in like, “Paul was a basket case at home, but it was about emotions. Work at the office was about facts and figures, and he was good at that.”
For those who struggle with relationships, they’ll understand him more. Those who don’t struggle, know someone who does. You’ve not only told the reader something about your character at the right time, you’ve made him relatable.
In a mystery, the same can work with a villain. Just remember you don’t want to overuse the slow reveal, or it will take on a soap opera effect. You also don’t want to use the same methods to introduce all of your characters in each story. Sometimes it’s as simple as telling someone, “He needed a haircut. His curly blond hair was now tickling the back of his ears. My brown eyed boy also had to brush it out of those eyes every morning when he got up.”
Don’t worry about getting it right every time, you won’t on the first draft. You’re writing for in 30 days, not publishing in 30. You’ll have time to edit, rewrite, get opinions, make corrections, and then complete. Whether it’s for publishing, or for accomplishing a private goal, you’ll get there.
Writing, like characters, reveal more as you write the story. The reader learns about the characters, maybe a lesson about themselves, and the writer learns how to impact others through their words. Character design isn’t about selling your character, it’s about connecting with the reader.