A common cause of accidents is changing lanes when another car is driving in your blind spot. The funny thing is that side mirrors were designed to eliminate this problem when they're angled correctly. You were probably taught to adjust your mirrors to the point where you see a small portion of your own car, but that's totally wrong.
To eliminate blind spots, angle the mirrors outward until you create a smooth picture with no gaps and no overlap between your side mirrors and rear-view mirror. It will seem strange at first, but now you will never lose track of a car in the other lane!