Fill out the top of the form. Identifying yourself is optional and you may feel more comfortable remaining anonymous if you plan on offering any criticism. Be sure to identify the class section and spell the professor's name correctly.
Answer the questions in the form. Some questions may ask for "yes" or "no" answers, while others ask you to elaborate about the course. Your feedback may affect the manner in which the professor teaches the class the following semester or academic year.
List two or three things that you feel might improve the course next time the professor teaches it, if necessary. Chances are there will be a question that asks you to offer such criticism. It need not be framed negatively. Perhaps you feel the professor should devote more time to a certain topic or include more information on another. You may criticize the amount of homework the professor gives or find that she doesn't spend enough time discussing the homework.
Clarify yourself by summarizing your overall experience with the professor if there is an open-ended question asking for additional comments you may want to make. You can use this opportunity to make sure any negative criticism you offered is explained in a more positive context so that it doesn't seem like you are simply a disgruntled student who is seizing the evaluation as an opportunity to seek revenge.