Eliminate your blind spots

To eliminate blind spots when driving, set your mirrors this way:

Sitting in the driver's seat with your window closed, lean as far to your left as you can (with your head right up against the glass), then set your driver's side mirror so that you can just barely see the side of your car in the reflection. Next, lean to your right until your head is directly in the center of the car (in line with the rear view mirror). Set the passenger mirror so that you can barely see the right side of the car in the reflection.

What you will find when your mirrors are positioned this way is that you will have absolutely no blind spots as you drive. To verify this, look in your rear view mirror at a car as it approaches you in an adjacent lane on your left. Just as the car begins to leave your rear view mirror, you will see it entering your side view mirror. For a short period of time, you will actually see the car in both mirrors at once. As the car comes closer and begins to leave your side mirror, you will already be able to see it in your peripheral vision on your left. The same holds true for traffic on your right and the passenger-side mirror.

When you first try this, it may seem unsettling if you've been trained to set your mirrors the standard way like everyone else. It's particularly disconcerting when rounding curves, but comfort will come with time, along with the confidence that you have a better sense of the traffic that surrounds you. You'll no longer have to turn your head (and divert your attention from the traffic in front of you) to see if anyone is driving alongside you.

It nearly goes without saying (although someone will probably get into a wreck because I didn't) that British drivers and others who drive on the left side of the road will adjust their right and left mirrors accordingly.

They can be purchased at most hardware stores that sell car gadgetry.

However, a word of warning: instead of turning your head when changing lanes, you must now look in two mirrors: the (overhead) rear view mirror, and one of the two side ones. You still can't change lanes safely based on what you see in the side mirrors alone. This is because you are, in effect, moving the blind spots of the side mirrors behind, in an area that is now covered by the overhead mirror.

Doing this makes it nearly impossible to see where your wheels or bumper is. Should you be hauling enough junk to block completely your rear-view mirror, be sure to adjust your side-view mirrors accordingly. Mirrors set this way can also make parallel parking rather difficult, depending on your vehicle and how well you can already parallel park. It should also be noted that even when you set your mirrors up this way, do not rely on it solely. It is possible for a very small car or a motorcycle to slide into the small blind spots that remain. This can be a very bad thing.

Footnote: Here I thought I was a genius when I figured this out one day...and I thought it'd be a great thing to node. And here I find Mshadow and RevJim23 beat me to it.