your/you're

From a teacher's perspective, this one's a classic. I'm not sure whether or not any pair of words is more often misused.

"Your driving me crazy," and "Is this you're book" are examples of sentences teachers see day in and day out. I would assume this is the kind of thing that drives many of them into early retirement.

If you're trying to figure out which one to use, the solution is simple. Since "you're" is a contraction meaning "you are," just say the phrase in the sentence. If it makes sense, use it. If it doesn't, use the pronoun version, "your."

Let's use the examples above. Does it makes sense to say, "You are driving me crazy"? The answer is obvious; therefore, use "you're."

Does it make sense to say, "Is this you are book"? Not only does it make no sense, it's just plain stupid.

The same problem exists with "their," "there," and "they're." That's an issue for a different time. I can only handle so much stupidity for one day.