Mind mapping diagrams begin by writing the main idea in the center of the page with a circle around it. Centering is important because once the diagram is finished it will resemble a tree. The center acts as the trunk. When you write the main idea, it's helpful to use a color you associate with it to help your brain bring another level of association to it. This method was originally used by Leonardo DiVinci to organize information.
As you discover more sub-topics, represent them by lines that radiate from the center subject and write these sub-topics on each line. Anytime you think of additional material that relates to each sub-topic, draw a line extending off of it and label that line. It's helpful to print your information in upper or lower case letters for emphasis and to make your diagram more visually stimulating. It's also better to make each line only as long as the sub-topic itself for easy readability.
Visual stimulation makes mind maps more effective at first glance, and using colors makes the sub-topic lines stand out thus giving them visual, as well as intellectual, meaning. Using colors also activates the right side of the brain, which results in using more of your brain when you are dealing with the main idea of your mind map. If you use mind maps repeatedly, for the same reasons, like studying, using the same colors for classifications like dates or theories, helps you make consistent associations.
Mind mapping is only effective if you can make sense of the finished product. Although it's a good idea not to limit your ideas, it's important to edit when you're deciding what actually makes it on to the page. It may seem clear immediately after making your map, but if you put it down and come back to it, it could prove to be confusing. It will help to use a separate sheet of paper to write down preliminary ideas as fast as you get them, and then begin to edit.