Witnesses are advised to prepare for the trial by reading the file a day before and again on the morning of testimony, by examining any physical evidence that is to be introduced, and by discussing the case with any other witness who was present. Suggestions are given on personal appearance and grooming, on overcoming fear on the witness stand, and on appropriate conduct at the counsel table and on the witness stand. Witnesses are advised to conduct themselves in a serious, objective, and businesslike manner at the counsel table and to speak loudly, clearly, and with conviction on the witness stand. They should try to avoid nervous habits and should maintain eye contact with the attorney asking the questions, the jurors, and the judge. The article describes the process of testimony during a criminal case, three key differences between direct and cross-examinations, and additional points that witnesses should consider when testifying. Common examples of witness behavior that could endanger the credibility of their testimony are listed, such as deception, bias, dishonesty, misconduct, and unfair conduct. A courtroom chart and a dialogue that illustrates common tactics of the adversary counselor are included. Ten references are appended.