WHO AND WHOM USE:
"Who" is the subjective form of the word, meaning it should always act as the subject of a sentence or a clause within a sentence.

Example: Who wants ice cream?

"Who" is the subject of the sentence and thus should be in the subjective form.

Example: For whom are you searching?

"Whom" is the object of the preposition "for" ("you" is the subject), so it should be in the objective form.