It is crucial to understand the difference between a subject and a topic when writing a research paper. Many students can easily come up with a subject, but often have a difficult time formulating a topic. What's the difference?
Let's say you are taking an American history class. The subject of the paper will obviously be American history but that is still way too broad. You decide to focus on James Madison. This is a little more specific, but James Madison had many historically significant roles in his life: this is still more of a subject than a topic. You decide you want to focus on James Madison's presidency as opposed to his work during the Constitutional Convention or as Secretary of State under Thomas Jefferson. Now you are getting closer to a manageable topic but you still need to focus on some aspect of his presidency. You decide to look at the War of 1812, and begin to research. As you do some research you begin to learn more about Madison's approach to managing the war, and the more you learn the more topics come to mind: you might discuss his administration's relations with Native Americans, and from there you might focus on a particular tribe or a particular tribal leader or a particular battle involving a particular tribe, or whether a particular tribe allied with the British or with the Americans, etc. The point is, you inevitably start with some broad subjects you are interested in pursuing and, as you find out more information about those broad subjects, more focused topics will come to mind. When you write your paper you need a topic that can be covered in the space of a paper: do not pick a topic that is so broad that you could only cover it in a book, unless you are writing a book (which most of your are not).