Prewriting is not about writing; it is about thinking.
First, consider your topic. Read the assignment/topic several times. Find out exactly what your instructor is asking you to write about.
Secondly, think about the topic. For example, if your instructor assigns a paper asking you to agree or disagree with current gun control laws, then you need to research the current gun control laws and find out why you do or do not agree with the laws. You may both agree and disagree as long as you create a logical reason for your response within your paper and back up your assumptions with reliable resources.
However, if your instructor gives you a broad topic, such as "business ethics" then you must narrow and define your topic. You might begin by thinking about the part of business ethics that most interests you. You could list two or three examples. You might think about a personal incident in your own life where your personal ethics were challenged by a business situation. After thinking about the issue, you might decide that you want to explore the need of businesses to establish a code of ethics that they can then convey to their employees and the community at large. At this point you are still exploring your options. You should not feel "locked in" to any certain idea.
You also need to look at reliable sources as you form your thesis statement. Simply searching Yahoo.com regarding your topic will not yield the most well-informed opinions or information. Although a Web search can certainly be part of the brainstorming process, ultimately you need to cite information from people who have earned credibility. You can cite CEOs of companies, Ph.D.s who do research in the area you are investigating, or individuals who have proven themselves over time in their industry and have thereby earned the respect of others in that field or business. Magazine excerpts from Time, Life, or People magazine are not considered reputable sources for academic discourse, nor are similar online magazines.
Finally, you need to create a working thesis. A thesis is first and foremost a "claim" statement. You are positing an idea or hypothesis, and you will develop that claim in the body of the paper. It may help you to begin a thesis by filling in the blanks of the following sentence.
I believe that ______________________ because ______________________.
For example, you might write: "I believe that businesses should develop a code of ethics because it will increase employee job satisfaction, provide a written standard of behavior for employees, and create a standard for interaction in the community."
For example, "I believe that current gun control laws are not effective because criminals will always have access to guns, many guns are purchased illegally, and such laws violate the first amendment."
It is important to have a "working" thesis before you begin writing a rough draft. Without an idea of where you are going, your paper will lack direction, specificity, and cohesiveness. However, remember that your thesis is a "working" thesis. If you change your mind about the thesis during your drafting, then simply change the thesis and adjust the draft accordingly.