Prewriting is the process of planning and outling information so you can become more familiar with your topic in order for your writing to be more effective.
A good prewriting strategy is developing a concept map. It will show how ideas related to your topic fit together. You begin by putting your topic in the center shape, and brainstorm other ideas that supprt the main subject by placing them in the outer shapes.
In most cases, your concept map will help you devise a clear and concise research question. A research question helps you keep a tight focus on your topic as you sift through the literature. You will be able to easily idenify material that supports your question and reject material that is irrelevant.