Know your rights: If your car is stopped by a police officer

Things are different if you are pulled over while driving than if you are simply stopped while walking down the street. If your car is stopped by a police officer, keep your hands where the officer can see them. If you are driving, you must show your drivers license, registration and proof of insurance...if you are asked for them (which you most likely will be). Therefore, it is really important to make sure that you have these things in your car, because failure to produce them may result in an arrest.
Officers can also ask you to step outside of the car, they can also separate passengers and drivers from each other to question them and compare their answers, but nobody legally has to answer any questions.
The police cannot search your car unless you give them your consent (which you do not have to give) or unless they have "probably cause" to believe that criminal activity is likely taking place, that you have been involved in a crime, or that you have evidence of a crime in your car. So, if you know you have nothing incriminating in your car, it is really up to you as to whether you consent to the search. Note that it may make you look suspicious if you say no, and that it will be humiliating if you say yes, so weigh the options quickly.
If you do not want your car searched, (assuming that the officer does not have "probable cause") clearly state that you do not consent. The officer cannot use your refusal to give consent as a basis for doing a search. And if possible, state your lack of consent so that others can hear and witness it, (but not obnoxiously or incriminatingly).
The protocol for a passenger is quite different though, and we will address it at another time...
Information provided by the American Civil Liberties Union.