You'll need to spend quite a bit of your prewriting time thinking about the best kinds of evidence to support your case. Remember that not all personal experiences or research materials are persuasive, the experiences we've had (or that our friends have had) may not be representative of a universal experience and consequently may lead to unconvincing generalizations. Even testimony from an authority may not be convincing if the person is not speaking on a topic from his or her field of expertise; famous football players, for instance, don't necessarily know any more about panty hose or soft drinks than anyone else. Always put yourself in the skeptical reader's place and ask, "Does this point convince me? if not, why not?" (For more advice on the selection of evidence, see the section on critical thinking in Chapter 5.)