The topic is generally chosen from one of the chapters in the text. However, narrow it down to a more specific topic than just the chapter name. For example, if you are specifically interested in adolescence, you could research "How peer pressure affects youth," "How substance abuse affects adolescent decision making," or "Stereotyping adolescent's and it's affects on self-worth."
So first choose an area of human development that interests you and then try to narrow it down.
The paper should be between 10-12 pages. However, if it runs over, that will be fine. I would like students to focus more on content rather than page numbers.