The second question would be the best to help identify the theme. For example, if a story is set in the 1800's, and the main character is a woman, you must think about how women were treated back in those days, and how little rights they had. Put yourself in their mindset. If the woman is black, the main theme of the story may deal with slavery or the unjust treatment they had to deal with back then (good vs. evil, power & corruption, etc.)