Who and Whom are often confused. One way to resolve the confusion on using who vs. whom is to remember that who is always used for the subject and whom for the object.
In particular, there are two scenarios that lead to a confusion between who and whom: when introducing a question, and when introducing a dependent clause.
Comparison chart
 | Who | Whom |
|---|---|---|
| Part of Speech | "Who" is always the subject. | "Whom" is always the object. |
| Example | Who are you? | Whom are you with? |
Who vs Whom when introducing a question
The rule that who should be used for the subject and whom for the object also extends to scenarios when the word is being used in a question. When the answer to the question begins with a subjective pronoun or noun, use who. For example, Who was the journalist who threw a shoe at George Bush? (The answer would be Muntadar al-Zeidi was the Iraqi journalist who threw a shoe at him. In the answer, Muntadar al-Zeidi is the subject so the usage of who is correct.)
On the other hand, if the answer is an objective pronoun (or noun), use whom. For example, Whom did you support in the presidential election? (The answer would be I supported Ron Paul. In the answer, Ron Paul is the object and so the usage of whom is correct.)
Who vs whom when introducing a dependent clause
The rule that who should be used for the subject and whom for the object also extends to scenarios when the word is being used to introduce a dependent clause. When the pronoun is the subject of the dependent clause being introduced, use who. When the pronoun is the object, use whom. For example,
- She is the only person in the town who stood up against injustice.
- The winner of the Man Booker prize was not the author whom I expected.
More Examples
- Research has shown that women who get pregnant when teenagers earn substantially less money over their lifetime than those for whom pregnancy does not occur until much later.
- To whom did you speak about extending the deadline?
- Robert, whom we all knew and loved, passed away this morning.
- Robert, who was popular and well-loved, passed away this morning.
- Our material culture often misguides children about whom to respect in society i.e. the rich rather than the honorable.
Lay 
That 
Advice 
Affect
Comments: Who vs Whom