boston.com has an interesting (read: trite) slide show of how to behave when you are pulled over by the police. Most of the advice falls into the “behave reasonably” category, but I object to one part: the idea that you should leave your registration in the glove compartment until asked for it.
Usually, the police run your license plates before approaching your vehicle. You can use that time to get your registration out of your glove compartment and your driver’s license out of your tote bag or back pocket. First off, you’re a grown adult and presumably know that you’re going to be asked for those items; having them at the ready is normal. Moreover, that saves you from having to grovel to the police officer that you’re going to be reaching into your glove box (where some people keep their guns) or your back pocket/tote bag (ditt0). Obviously, have your hands in plain sight when the police officer approaches the car, but there’s nothing wrong with having those items at the ready.