I don't know what era your cop buddy gave you that advice, but it most certainly does not apply in 2018. There have been too many people who exit the car and immediately start shooting. The officer would you rather stay in the car with the door closed, which limits your ability to target the approaching officer.
The proper response is to pull over safely, turn on your hazard lights, fully lower your window (both windows if there is a second officer and you have power windows,) turn off the ignition and place the keys on the dashboard, keep your hands on the wheel at 2 & 11 so the officer can clearly see them, and do nothing else until requested.
Do not lean over to your glove box to get out your registration and proof of insurance until you are asked to produce them. If you lean over to your glove box while the officer is approaching your vehicle, expect to have a gun in your left ear when you sit back up again.
Be calm, be polite, and be compliant. It is safer for all concerned.
“I don’t know what era your cop buddy gave you that advice,”
About 1969 - 1970. That far back I can’t remember for sure.
I have been told that the Highway Patrol in Texas will stop at your back bumper and tell you to step out of the car. Since I’ve never been stopped by them, I can’t say I know that for sure.