The character traits of your protagonist can come from a variety of sources. Your imagination plays a role, but also interactions with people who have qualities you want to use. My own technique didn’t come from any writing class or by reading the newest ‘How To’ book, but it has fit in with the way I go about constructing a story.
Here’s the process I used in creating my first protagonist:
1. What are the positive traits?
Sees the world differently than most
2. What about negative traits? My main character would be rather boring if he had everything going for him. Flaws in a character add to the difficulties they may encounter in solving whatever problem that is the focus of the novel. My character had these to contend with:
Notice there may be a trait that is listed in both lists. My protagonist thinks in pictures, which can help or hinder his goal.
3. Develop the story around both descriptive lists. What problem is my protagonist trying to solve? How will I use these traits to help or hinder achieving his goal?
4. Identify where in the story arc I want to introduce each. Most of mine were introduced in the first 25% of the story.
I do a similar positive/negative ‘T’ chart for each of my other characters. It’s like a puzzle and through rewriting, critiques, and time, the pieces finally fit together.