This is an especially fun exercise to do with a group. For this exercise, Imagine your main character looking out a window, either at his school, home or other location where he spends a lot of time. Write about what he sees and how the scene outside his window impacts his emotional state. Does it create a longong, resentment, despair? Write for 15-30 minutes.
If you are doing this as a group exercise, discuss how your intent as a writer may or may not intrude upon what your character sees, and your influence on your character's emotional response.