Brainstorm topics that you find interesting. If you are already in a psychology class your instructor may give you a choice of topics from content that you have covered. In this case, make an organized list of topics and considered which ones pique your interest. You can begin narrowing your topic from this list. Some topics you might consider include theories of developmental, cognitive or organizational psychology; the history and ethics of experimental research; theories of the mind and applications of modern behaviorism.
If you have a topic and are unsure if it is acceptable, discuss your ideas with your instructor. It is her job to help you with these types of problems. She can also let you know what she is expecting from the paper, which will likely help you to narrow the topic.
Test your topic ideas. Once you have narrowed your interests, formulate your topic in the form of a question. For example, you could ask: "What is the purpose of an internal review board in psychological research?"
Formulating a question will help with the overall paper as well. If you have a clear research question, your paper can take the form of answering that question.
Test your questions by researching them. Select key words or phrases related to the question and conduct a search of your school library's catalog or use your school's research database. If you find too little information on your topic, then you need to broaden the topic. If you find too much, you will need to narrow it. For instance, you can broaden the question to: "What are the steps in creating a research design for psychology?" Or narrow it to: "What are the ethical concerns addressed by internal review boards?" Or, "What is the purpose of internal review boards in experimental behavioral psychology?"
Narrow and evaluate your topic. Once you have done some research on your topic, you will have a better sense of what that topic involves and what the dominant discourse in that specific area is, and then you can choose what direction to take your paper in.
For instance, if your topic is the history of developmental psychology, you might begin by researching specific theorists.
In narrowing your topic, consider whether or not it is researchable given the length of the paper. A broader question may require a longer paper to answer it. Consider what type of information you need to answer your proposed question. For instance, you may require statistics or results from experimental studies, or you may need to find case examples that discuss the theory behind a specific treatment. If you decided, for instance, to compare the work of Jean Piaget and Lawrence Kohlberg (two developmental psychologists), you might look at historical information about their theories as well as modern experimental studies that either support or refute these original theories. This information should help you narrow the topic, for instance, to comparing the theorists' points of view with regard to cognitive development.