Draw from your personal interests. If you and your family often take mission trips to Latin America during the summer with your church, develop a topic that would inform the audience about various aspects of poverty in a particular Latin American country you visited. Discuss the stories the native residents told you, and talk about how these trips influenced your views on poverty in the world.
Research current issues. For example, if your health teacher recently discussed the consequences of an overabundance of fast-food restaurants and not enough outlets for affordable and healthy food stores in low-income neighborhoods, do further research on it and develop a speech based on what you found.
Get inspiration from people you know. If your great-grandmother lived through the Great Depression in the 1930s, get a voice recorder and ask questions about how she handled adversity in her life and what advice she has for you that you can carry with you as you get older. During the conversation, take notes then write your speech based on those notes.