Most people don't angle them out far enough, and thus, they suffer from blind spots that are larger than necessary while the field of view of the inside rear view mirror overlaps that of the outside mirrors unnecessarily.
To do it properly:
Begin with your seat adjusted properly.
Lean your head all the way to the left, against the side window glass, then adjust the left outside mirror so that the side of your car is just barely in view at the inner edge of the left outside mirror. Most (90% - 95%) of the mirror should still be showing you the world outside at this point ... not the side of your car.
Then lean the same amount towards the center of the car, your head should be almost over the console, and adjust the right outside mirror so that the side of the car is just barely in view at the inner edge of the right outside mirror.
Now, when you look back, there will be minimal overlap between the inside mirror and the outside mirrors. When someone is in the adjacent lane, they will come into view beside you before they disappear from view in the mirror.
People who are not accustomed to having the mirrors like this might find it a bit odd, but after a while, the almost absence of blind spots will be great.
It still doesn't eliminate the need for shoulder checks, because motorcycles might still be able to fit in what little blind spot remains, and on multilane roads, you still need to check for vehicles two lanes over that are going for the same spot that you're looking for. But it's a lot better than the way most people have their mirrors.