ARRIVE AT THE CONTROLLING IDEA 
from The Dump Ground by Wallace Stegner CHOOSE A SUBJECT AREA. Writing a long composition of several paragraphs requires the careful selection of an idea that you can adequately discuss. It's tempting to think that because you are writing a long composition,  you can choose any subject,  no matter how broad.  But it is important to limit the idea to a  very specific topic.  Once you have done this, you must consider two very important factors:  the meaning the topic holds for you, and the meaning you intend to bring to your audience. As you're deciding what you want to discuss, it's important to make sure  that whatever you choose holds interest for you! You can't  interest your audience if the topic doesn't interest you  as well!
DETERMINE THE SPECIFIC TOPIC.  Although Stegner chose the the subject area of town dumps, he obviously could not write about all town dumps, or even about all aspects of one dump. He might have chosen the specific topic of the town dump and health, or the town dump and unsightliness. Instead, he chose the aspect of the town dump and the town's history.  In the same fashion, you must narrow a general topic to one that is more specific; in this way you move toward what will become your controlling idea.
STATE YOUR CONTROLLING IDEA.   Once you have decided on a controlling idea it is important to turn that idea into a concrete statement.  Just which aspect you select depends both on your interests and the interests of your audience.  Unless you have a specific audience in mind, try to appeal to the largest possible group, to the general reader.

ASSIGNMENT.  Each of the following subject areas could be turned into a good paper, but they need to be narrowed down. Change each of the areas into a specific topic. Then, using a complete sentence, write a controlling idea for each topic.  Finally, choose one of the topics and write a paragraph in which you discuss how you would develop it into a longer paper. Remember to include reasons for your interest in this particular area, the specific audience your paper is geared toward, and any details you would include in your writing.