1. Never consent to a search. Not of your car, your house, nor your person. Tell them that you do not consent to any searches. They'll make shit up about how you'll get in trouble, but cops are allowed to bullshit you. You aren't allowed to lie to them, but they can lie to you all they want. Most people get in trouble because they let the cops search something that they had a constitutional right to keep private (is this where all those 4th Amendment jokes come from, TBW?).
2. Say you're pulled over and asked to step out of the car. You can ask if you are free to go or if you are being detained. They normally aren't allowed to detain you.
3. When pulled over, ask the officer why you were pulled over. I made this mistake when pulled over in Mississippi and waited about 10 minutes before the officer told me why he pulled me over.
4. Shut the fuck up. I talk too much. They'll try to turn your words against you. An example of this is a "compound question" such as: You don't mind if I search your car; you don't have any drugs in there, right? If you answer no, then you don't mind if they search your car, even if you meant that you don't have any drugs. If you answer yes like you mind if they search then you sort of just got trapped into admitting that you have drugs in your car and that allows them to search by giving probable cause.