You can't see behind your car using your wing mirrors, you need to use the rear-view mirror. Even if you have the wing mirrors pointing behind your car, the sides of the car obscure your view.
I like to adjust the wing mirrors so that a tiny sliver of the car is visible in the mirror, that way I can be sure I'm not missing anything.
What you do is "normal". The suggestion from the comment I replied to is referring to the "new" way referenced on the linked page, where the mirrors are set wider.
I like to adjust the wing mirrors so that a tiny sliver of the car is visible in the mirror, that way I can be sure I'm not missing anything.