English and ESL Instructor
Who put this on my desk? (He/she put this on my desk.)
Whom do I give this to? (I give this to him/her.)
This same rule applies for "whoever" and "whomever":
Whoever wins the competition gets $1000. (He/she wins the competition and gets $1000.)
I will give this to whomever needs it. (I will give this to him/her.)
In spoken English, many people do tend to misuse "who" for "whom", but in written English, it is important to remember the distinction between the two:
Who do I contact if I have any questions? (incorrect)
Whom do I contact if I have any questions? (correct)
Now that you have a clearer idea how to use "who" and "whom", see if you can figure out the meaning this joke:
A: Knock, knock!
B: Who's there?
B: To who?
A: To whom.