In my experience answering grammar questions, pronouns give people a lot of trouble; so you are not alone. Both who and whom are relative pronouns instead of being just plain, ordinary pronouns (Actually ordinary pronouns are called personal pronouns). In addition, who is also an interrogative pronoun, while whom is not. But that is not really the question you ask. BR>Who is usually used in a sentence with a subordinate clause where it becomes a stand-in for the subject noun in the main clause. Here is an example: Sally, who was at the mall that day, saw me. “Sally saw me” is the main clause, even though it is bisected in two with the subordinate clause, “Who was at the mall”. In the subordinate clause, “Who” stands in for the noun “Sally.” The important link between the noun Sally and the pronoun Who is that both are subjects.

Whom, on the other hand, is a object pronoun, so it stands in for nouns in the object position.

Here is an example: Dr. Benton is the surgeon whom we recommended. Studying this sentence, we see that “whom we recommended” is the subordinate clause. We’re good so far. We also see that “Dr. Benton is the surgeon” is the main clause. But, in this case, the subordinate clause — “whom we recommended” — is different from Sally’s situation, because “Whom” is who we recommended. “Whom” is in the object position of the fact that “We” recommended. It still replaces the noun Dr. Benton, but it is the object of what we did . . . which was recommend him. You could turn this sentence around to say: “We recommended Dr. Benton, who is a surgeon” in which case you’ve changed “Whom” to “Who.” And this is perfectly all right, provided you have the grammar correct

So I hope you begin to see that pronouns can be manipulated to mean what you really want to say. The bottom line is to think about it, from the writer’s point of view, and make your prose as clear as possible. You are in control, if you know the rules.