The book Discovering the Writer Within talks about using your free writing to write bout someone you know, giving the person you know a real look about actions and reactions. My take is to do this with a character. Sometimes this is done by writing it down but most often I do this by thinking about the character. Take the young woman who occupies the center stage in my current WIP.
What do I know about her beyond the basics and that's where free thinking or writing comes into play. She is a Leo, a Fire sign and she has a tendency to act first and react second. Because she is young she ahsn't learned the controls an older Leo would have learned. So this impetuosity is what I want to explore. She hates to wait.
During this session, I began to think about what disaster her leaping into action might cause. What would be the cause? Boredom and feeling as though something must happen. I explore this avenue for a time and the situation begins to come to a head. She acts im her usual way and then the question becomes What are the consequences of her action? This adds more depth to the scene I'm developing and brings her character into focus. By doing this with no real plan I've come up with a scene that adds depth to her character, that advances the plot and brings a complication to the hero.
From there I can free think or write what happens with the hero, also a Leo but one who has a different emotional reaction to events.
So use a bit of free writing or free thinking to go beyond your story and who knows what might develop with your characters and your story.