Creating a character is a responsibility that I don't think all writers take as seriously as they should. They just throw a name out there and give their character a stereotypical cardboard cut-out persona. What if you were a character in someone's story? Would you be content being turned into a stereotype? There are many things that make you who you are. Would you be content as a cardboard, predictable character with no depth? I doubt it.
I'm about to create a life, giving birth so to speak. Not quite as painful as childbirth but I still might get a writer's cramp!
Meet Jimmy Anderson. How do you see him? What if I told you he was a young man? Did your idea of him change? Writers don't take advantage of the power they have a lot of times. Unlike a parent that must almost take a gamble and take what they get (not dissing that at all, I applaud God's decision making there), I can form Jimmy how I want. I can even skip all those messy, loud baby years and those "terrible teens."
Jimmy is a 20 year old man, going to college. He works at the local grocery store -- though feels it's too mindless -- while being a full time college student. He wants to be a sports reporter after graduation. Jimmy's average in height at about 5' 10" and he’s around 200 pounds. He was a football player in high school; all 4 years (see what I did there, gave him a past but didn't have to live it). Football damaged his left knee though, and sometimes he wakes in the morning with intense pain yet refuses to get it checked out. Jimmy says that makes him tough and his stride gives him character. His best feature is his hair, blonde and long. Not quite long enough to be a mullet so he jokes it's a party all around.
From that one paragraph you have a better view of Jimmy, don't you? Was it your view of him, how much did it change? What can you deduce from that paragraph about his character? What are his values, feelings, and persona? Being able to give readers a good view of each character (and in some cases telling them some things without spelling it out) is a gift that many writers don't know they have. Also being able to do that with limited space (almost being both flowery and concice at the same time) is true writing talent. You don't want to bury the narrative, but still paint the picture. Show, don't tell.
Get away from things like: Jimmy was a blond guy that goes to school and works. That's what I see so often and needs desperately to be expanded. Describe how you see him in your head, or answer the questions from the paragraph above in comments.