My advice to clients when involved in a traffic stop. Be polite and professional. Do not argue with the cop. Answer questions as briefly as possible. Concentrate on what the cop is saying. Keep track of how long the stop lasts. Politely decline to take any tests or to allow any searches of your vehicle. Get to me as soon as possible after the stop to tell me exactly what was said and done. Any argument about the stop will be done by me in Court, where it matters.
Caren Turner, ex Ethics Commissioner for the Port Authority of New York and New Jersey gives us a great example of how not to handle a traffic stop (strong language advisory):
Way to go Caren for turning a meaningless traffic stop into a life altering calamity for yourself! Give her a hand ladies and gentlemen for giving us all an example to avoid!