Know Your Rights
The First Amendment guarantees you the right to free speech, however, when dealing with the police you are safer exercising your Fifth Amendment right to remain silent. The police are not your friend, though they will try to convince you they are.
ANYTHING YOU SAY CAN AND WILL BE USED AGAINST YOU AT TRIAL. This especially applies if you have NOT been read your rights. The police only have to read you your rights if they plan to interrogate you, but ANYTHING YOU SAY CAN AND WILL BE USED AGAINST YOU AT TRIAL.
The Fourth Amendment protects your right to privacy in your person, in your home, and in your belongings. DO NOT consent to a search of your person, car, home, or belongings. The Supreme Court has determined that if the police are engaged in a consensual contact the rules that we are all familiar with do not apply. A consensual contact is when the police determine you are free to leave or end the conversation, yet they do NOT have to advise you that you are free to leave or end the conversation. You must be proactive in your determination that the contact is NOT consensual. You can accomplish this by continuously asking, "Am I free to leave?"
There is a free app on the iTunes store and on the Google play store called "The Oh Crap App". I recommend it to everyone with an Apple or Android device. It is customizable to include your information and the information of your attorney. When approached by the police, simply press the button for the app and it automatically starts recording the contact.