"To whom," brother! "To whom," brother! "To whom," brother!

One of the more confused issues of grammar is the "Who" vs. "Whom" usage. "Who" is nominative case, while "whom" is accusative case.

Rule: Use the he/him method to decide which word is correct.

• he = who
• him = whom

Examples:
Who/Whom wrote the letter?
He wrote the letter. Therefore, who is correct.

For who/whom should I vote?
Should I vote for him? Therefore, whom is correct.

We all know who/whom pulled that prank.
This sentence contains two clauses: We all know and who/whom pulled that prank. We are interested in the second clause because it contains the who/whom. He pulled that prank. Therefore, who is correct. (Are you starting to sound like a hooting owl yet?)

We want to know on who/whom the prank was pulled.
This sentence contains two clauses: We want to know and the prank was pulled on who/whom. Again, we are interested in the second clause because it contains the who/whom. The prank was pulled on him. Therefore, whom is correct.

• Source: GrammarBook.com