Your choice of a suitable research subject is often determined by whether or not you are interested in reading or investigating. Investigating the primary sources puts you in the role of a detective and is best paired with the subject that you have developed an intimate preference. Working with secondary sources is allows you to see the larger picture by analyzing what others have said about your topic.
The typical research paper involves the latter; you are expected to do a fair share of library research. Many people, who are wondering how to write a research paper, also need to be critical on the topic choice. Not only it should be interesting, it also must be suitable for academic level. Some subjects are not worth investigating; they are too trivial, merely factual, or too routine. Others are often too new or current for a conclusive study.