The best thing to do is to stay calm and quiet if you are pulled over. The Fifth Amendment’s right against self-incrimination permits an individual to refuse to disclose information that could be used against him or her in a criminal prosecution. Nothing you say can possibly help you. You should be polite with the officers, don’t consent to a search of the car, and simply state that you do not wish to make any statements.
A vehicle can be searched if police has a warrant or the search falls under an exception to warrantless searches. Some of the exceptions include: consent, automobile exception, search incident to a lawful arrest, plain view/plain smell, inventory search. Please review “When can police stop and search my vehicle?” for explanation of each exception.