This step is very important. Pick a subject/topic that interests you. You'll find the research process less tedious, and the writing process more natural. A narrower topic is often easier to research and write about. You'll have a clearer idea of what you want to say, and you'll be able to develop your ideas fully without becoming overwhelmed.
What follows are some examples of subjects narrowed down to manageable topics. You should also begin to formulate a working thesis. This is an opinion about your topic that will serve to focus your research.
Note: A working thesis will no doubt change as you research your topic. This is OK !
Social Studies Example
Subject: The American Civil War,
Topic: The Effects of Guerrilla Warfare in Missouri on Civilians.
Thesis: Brutal guerrilla warfare caused the massive depopulation of rural Civil War Missouri
Science Example
Subject: Genetics
Topic: The Misuse of the Humane Genome Project
Thesis: Scientists who use information from the Human Genome Project for cloning purposes threaten the sanctity of life.
Language Arts Example
Subject: The Romantic Era in American Literature
Topic: The Influence of the Transcendentalists on the Modem Environmental Movement
Thesis: The Endangered Species Act is a practical application of the writings of Emerson and Thoreau.
Since you don't know how much information will be available, pick a topic you can broaden to a wider range, or narrow to something more specific. If you are finding tons of information on your topic, narrow it to something more specific and manageable. If you are not finding enough, broaden it to include a wider range of information.
Examples
Topic: Hunting
Narrow to: Small Game Hunting in Colorado
Topic: Cruelty to Tigers used in Circuses.
Broaden to: Animal Cruelty in Circuses
In the second example, you can include other animals besides tigers, giving yourself more options. Generally it is easier to start with a broad topic and narrow it down.