Originally Posted by 62thunderbird
Adjust the driver's mirror outward until you can just see the side of your own car with your head against the door glass. Then adjust the passenger mirror outward to the point you can see the side of your own car when you are leaning as far as you can to the right.
The result will be that a car leaving your view in the rear window, will appear in the appropriate side mirror. and as it leaves the side mirror you'll see it with your peripheral vision in the door window. Try it: it works. It works on most cars actually.
Yes, most people have their mirrors turned in too far but then again, I remember being taught to set them turned in while in driver's ed. Very bad advice. The method described by 62thunderbird is a far, far better starting point for proper mirror adjustment.