friendly tip for the day...(or aka: I look this up on a regular basis, so I decided to make an anchor chart for us)

Whom should be used to refer to the object of a verb or preposition. When in doubt, try this simple trick: If you can replace the word with “he”' or “'she,” use who. If you can replace it with “him” or “her,” use whom. Who should be used to refer to the subject of a sentence.