Student or Learner
Does somebody know the rules to use whom?
"Tom hit whom?", "Whom did Tom hit?"
"To whom did you speak?"
"With whom are going to the movie?"
Wherever "who" is an object, it becomes "whom"
Now, I have to tell you very few people speak that way, and many people never say whom: they use who in all cases. At times "whom" sounds strange even to most prescriptivist ears, especially in informal situations.
"Who are you going with?; Who did Tom hit?; Who did you speak to?"
This varies by social situation, your listener, level of formality, and other social factors, that most people ignore anyway.