Here’s how it works.
First: Set your rear-view mirror the way you normally would. Then, lean your head all the way to the left so it touches the driver’s window. With your head in that position, set your left side-view mirror so that you can just see the back corner of your car. Now lean the same distance the other way, and set your right side-view mirror the same way.
Once your mirrors are set this way, when a car comes up behind you, you should first see it in your rear-view mirror. But as it passes you (let’s say on your left), you’ll see it move to the left side of your rear-view mirror. And as its left headlight disappears from your rear-view mirror, it should instantly show up in your left side-view mirror. This should happen instantly, so you can always see it.
Next: Double check your side-view mirror alignment. You can pull up next to a row of parked cars (to simulate passing traffic) to help this. Check your mirrors starting with the left: as soon as a passing car’s front left headlight disappears from your rear-view mirror, it should appear in your left side-view mirror. Then check the same thing on the right side.
That’s it! You may find that it takes time to get used to driving with your mirrors in this set up. You’ll need to start relying on your rear-view mirror first. But once you do, you’ll avoid the blind spot altogether!
Information courtesy of the National Safety Council