Cops never know what they are about to get into when they come up on a traffic stop. It could be a nice little old dentist from Connecticut who never drives over 55 except on Sundays - or it could be a serial killer with a fresh body in the back seat. If you can allay his anxiety a bit it accomplishes two things - 1) It relaxes him a little, making him more ameniable to the idea of just warning you. 2) It plants the idea that maybe you are part of the fraternity.
When I see the lights come on, I roll down the driver's side window and give a brief wave to indicate that I am aware of the officer. I also turn on my signal to pull over. I then continue driving until I get to a wide shoulder, a gore point, or an exit where the officer and I will both be safe. Pull over - way over. Windows down, engine and radio off, dome light on. Both hands resting on the steering wheel - and they stay there! When the officer approaches the car be polite and (if you can) friendly. When he asks for your driver's license, registration, and proof of insurance, tell him where they are located before you reach for them. I carry my wallet in a bag under the driver's seat. I tell the officer "My wallet is in a bag under the seat - may I reach for it?" If it was in my back pocket I would say "My wallet is in my right rear pocket - may I reach for it?" Until he says yes my hands don't leave the steering wheel. When I unzip the bag I make sure he can see in before I reach for the wallet - I don't want my hand disappearing. My movements are a little slower than normal. Same thing for my registration. "The registration and insurance card are in a book in the glove compartment. May I reach for it?" Nothing is done quickly, nothing is done without permission.