Do not play loud music
Similarly, if your music was on, turn it down immediately. You need to not only show respect for the situation and the law enforcement officer you are speaking to, but you also need to be able to hear each other.
Don’t reach for something in your bag
As a cop approaches your car he is watching your every move, not only to assess your situation and potential guilt, but also to determine his own safety. If you abruptly reach for something in your bag (even if it’s a piece of gum) the cop will assume the worst and may assume you’re looking for a weapon. Do not reach for anything in your bag or glove compartment unless the cop asks you to retrieve your license and registration.
Don’t be disrespectful
In life you should always treat others the way you would like to be treated. And that is especially true when it comes to interacting with police officers. Remember they are people too, and as with all authority figures, you need to treat them with respect and common courtesies.