Who and Whom Confusion

Here are some practice exercises:

http://www.chompchomp.com/handouts/wordchoice07.pdf
http://www.towson.edu/ows/exercisewho-whom2.htm
http://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-6923.php

Here are some rules:

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.