Being stopped by the cops is scary. This Instructable HowTo gives you everything you need to know to safeguard your rights when you are dealing with the police. All of the information is straight from the American Civil Liberties Union.
Think carefully about your words, movement, body language, and emotions. Do not get into an argument. Do not run. Do not resist. Do not complain. Remember officer badge and patrol car numbers. Write down everything you remember. Try to find witnesses.