Having given the character a name, one needs to look at their traits. What are their pluses and minuses. Every writer has a way of making this discovery. I happen to use Astrology to find mine.
What I really think about this is there are three ways a character comes alive. There is the face he or she shows the world. We've all known people who appear to be one way and yet are really perhaps not the opposite but they are different from what they let people see. What you see may not be what you get. These differences are what makes a character different from every other character in fiction and there are thousands of characters. So I list several traits each of my characters may portray.
There is the character's true nature. This includes the little secrets they keep inside, the things they don't want anyone to know. Or the things another character needs to dig to fine and give the character a second dimension. This comes to a character's heart. I once wrote about a character who seemed on the outside to be a decent and helpful person but inside he was someone quite different. And his inner self wasn't one you wanted to know.
All characters even the coolest ones have emotions and these emotions cause them to act. Maybe they respond to situations in a way different from their inner or outer natures. So I try to assign a few emotional traits that may or may not be in conflict with the character's natures. Reactions and actions are emotional responses.
So look at your characters and take them from the one or two dimensional creatures and make them three dimensional. Readers will see this and respond to your stories.