I myself have made confusion as well. So, back to the square one, on a new tack. I´ll try to keep it simple, so Marshall Rodrigues can grasp the concept. Indeed the HE/HIM method was correct, my interpretation/example was not.
With the structure Who/Whom did-does...
Somehow the “main” verb of the sentence/question, which will answer our question, is what will be
Determining the answer HE/HIM. The answer, in its turn will be what determines if we should use WHO/WHOM.
Who/whom did you meet in the beach?
1) Attention to the verb “meet”. Since I met him, it means that he “suffers” the action of the verb.
I was the one that performed the action, the agent. HE was the object of the action.
2) So I met HIM at the beach. The sentence takes WHOM.
3) Other corolary of (2) is, what raises my/our curiosity when we/I make the question is “HIM”
Who/whom did write the letter?
1) Attention to the verb “write”. HE now is the one that performed the action (of writing). “The letter” was the object and HE is the agent (the one that performs the action).
2) Thus, HE was the was the one that wrote the letter. The sentence takes WHO.
3) At the end of the day, what draws our attention in this case is “HE”
Who/whom does Sarah want to take to dance?
1) Attention to the verb “want”. He is vital to answer our question, too satisfy our curiosity.
Sara is the agent, the one that performs the action (want).
2) The answer is HIM, Sarah wanted to take HIM (not HE) to dance. The sentence takes WHOM.
3) What draws our curiosity at the very last, in this case, is “HIM”.
Complementary readings, but not compulsory, though.http://www.acadiaenglish.com/who-vs-whom/http://blog.oxforddictionaries.com/2013 ... at-debate/http://www.quickanddirtytips.com/educat ... advanced-0
All that, considering that it´s a question meant to be put in use in exams/tests or formal settings. In spoken/colloquial English the usage of “whom” is getting updated, to the point of being considered pedantic sometimes.
As for my comment on the Portuguese grammar, was because there are others learners that could benefit from the shared knowledge. And taking into account that Portuguese is our ultimate tool kit when we lack the proper words in English.
I took a conversation English course once, and even there, sometimes we used Portuguese as the last resource! (sometimes as the first…)
I am sorry for what happened, though. I didn´t know it was a touchy subject and it meant just a passing commentary. Nothing to hurt somebody, anybody.
Anyway, I won´t comment on your Portuguese from now on. I acknowledge that I was wrong, albeit unintentionally.
I know everything we wanted was just to help a fellow learner. So, let´s put the misunderstanding behind, for life is short. And a friend of mine once said “What do you prefer, to be right or happy?” let´s choose happy!