I think that the process of elimination is one the best things I have learned in high school. After doing countless tests and exams, the process of elimination sure helps to pass. Although this is not something they teach in the books, this problem solving skill is something everybody should have in their pockets. The process is not difficult to learn at all either. The process involves removing all other possibilities that cannot be correct, and by doing this, raises the probability that the correct answer will be within the choices left. Now that you know how to use it, I'll explain some uses for it.
First and foremost, you should almost always use this method whenever you are doing multiple choice questions on a test. 1 out of 4 is only 25% that you will get it right, but by eliminating 1 incorrect answer, you will have a 33% chance! By eliminating another answer you will end up with a 50% chance of guessing the correct answer. This shows that you don't necessarily have to know the answer to get it right, as long as you know what the answer isn't you can just work backwards.
A more ghastly use of the process of elimination could be to eliminate your opponents, allowing you to win at whatever you may be doing. Although most circumstances it would be illegal to do this, its a guarantee win. (unless you get caught :p)
There are many many more possibilities out there for using the great problem-solving technique. So just remember, every time you are stuck with a problem, try using the process of elimination.