Question 1

Is it "who should I call" or "whom should I call"?

Accepted Answer

Strictly, "whom should I call" — the caller is doing the calling to someone. You would call him, not he, which means the object form whom is correct. "Who should I call" is common in speech and rarely sounds wrong. Edited prose still prefers "whom."

Question 2

What's the difference between "who" and "whom"?

Accepted Answer

Who is the subject — it does the action. Whom is the object — the action happens to it.

Question 3

When do I use "whom"?

Accepted Answer

Use whom when the pronoun is the object of a verb or preposition — when something is done to it.

Question 4

Is it "who to blame" or "whom to blame"?

Accepted Answer

"Whom to blame." The blame is being done to someone — the object slot calls for whom.