Creating strong characters depends on putting feelings and emotions into words on the page. Physical traits and character backstory can help create a vivid character, but it is how they behave to a situation that really makes them come alive.
This emotion wheel can help you determine how a character will act in a given scene.
Is your character embarrassed? Does he feel ridiculed or annoyed? From the outside of the circle toward the center, he is feeling a mixture of sadness, anger, and disgust. How is he going to act? Will he lash out? Will he walk away? Will he swallow his feelings and extend a hand and a smile?
As the writer, you get to choose.
Looking for more help – check out this website for a cheat sheet on body language.