To increase your chances of a receiving a warning rather than a ticket:
Make it an easy stop. Pull over quickly, turn your interior lights on and keep your hands in sight on the wheel. When an officer approaches a vehicle, says Iowa State Patrol Sgt. Scott Bright, he or she will be looking at how many people are in the car and where their hands are.
Be respectful. If you were looking for a way to ensure a ticket, being argumentative, angry or rude is a great way to do it. "There is no guarantee that a driver will receive a warning based upon behavior," says Colorado State Patrol Capt. Jeff Goodwin, "but it certainly helps to be respectful and less confrontational."
Save the excuses. Law enforcement officers have heard them all, so save your sob story. Answers to any questions should be brief and noncommittal. (For example, if the officer asks if you know why you've been pulled over, say no, legal experts advise.) Don't argue. This isn't a court.