Button your lips, don't talk without an attorney present. The police are not your friends, don't buy the 'hey buddy, what's going on?' bonhomie crap.
I'm amazed at how many of them so freely give up their rights. Answering questions, willingly submitting to searches of their person or vehicle, and allowing themselves to be "detained" (with handcuffs or in a police car), before being arrested.
I fully support police officers and what they do, but I would not offer any of that, on principal.