Which is correct Paul and me or Paul and I?

Paul and I is correct depending upon the context. It is incorrect to say "The forms were sent to Paul and I," because the forms were not sent to "I," they were sent to "me." In this case you would say, "The forms were sent to Paul and me."

This is one of the most common mistakes people make, and you hear it even from people who consider themselves literate. The best guideline you can use is to eliminate (in your mind) the other person from the sentence. "Paul and me think the same way," is incorrect, because you would not say, "Me think the same way"; you would say, "I think the same way." And because you always put yourself last, you would say, "Paul and I think the same way." But you would not say Paul gave his way of thinking to my wife and I." You would say, "Paul gave his way of thinking to my wife and me." See?

Crestryder