Write your topic on the center of piece of paper and circle it. Everything in the paper will have a connection to this word.
Draw a few lines leading away from the circle. At the end of the lines write one or two words which summarize the central word. For example, if you are writing a paper about cats write the word cat in the center of the paper and circle it. On the lines leading away from the central word you would write major ideas people would need to know about cats like eat, sleep, live and reproduce.
Circle each word you write and draw lines radiating away from those words to further break down the category.
Write subcategories at the end of the lines and circle them. Repeat Step 2 until you have exhausted the topics you wish to write about in your paper. It is better to take on a little bit too much than to scramble for more information at the last minute.