The simplest way for you to approach this assignment is to re-read the chapter and make a list of each character and the new information. Here are some examples from the beginning of the chapter to get you started.
Jem- “Jem was twelve. He was difficult to live with, inconsistent, moody. His appetite was appalling.” (ch 12) Atticus says that Jem is growing.
Scout- Scout has trouble understanding the changes in Jem. Scout seems to be interested in the fact that Dill says he is going to marry her, but not much. She has trouble understanding both Jem and Dill, and feels like she is growing apart from both of them.
Atticus- He tries to show Scout how to be patient with her brother.
Mrs. Dubose- She has just died.
Calpurnia- She is sympathetic to Scout.
Dill- His father is a lawyer like Atticus, but younger (according to Dill). Dill tells stories to make himself feel better about his life.
Boo Radley- He stays in the house and cannot be coaxed to come out.
You can read chapter 12 here: http://www.wssb.org/content/classrooms/tate/content/sophomores/stories/to_kill_a_mocking_bird/Chapters/12.htm