Step 1: Start by setting your rear-view mirror as you normally would.
Then, lean your head all the way to the left so it touches the driver's window. From that position, set your left side-view mirror so you can 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.
Now, here's what happens. 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. There should be no delay. It should slip from one to the other, so you can always see it.