[CharacterCounts]

Your trick seems to work better for statements than questions.

He do you trust?

Him do you trust?

Which is correct?

[Erasmus]

Since you are using the interrogatory form, you can un-invert the word order and then it becomes clear:

Do you trust him?

vs.

Do you trust he?

[plusone]

Rework the questions. 'Do you trust him" or 'Do you trust he'.

[Emily RN]

Restructure your sentence to rephrase the question or make a statement. For example: Do you trust he? or Do you trust him?

[bannie]

He do you trust? Him do you trust? Which is correct?

Just as you do when you diagram a question, turn the question around.

Do you trust he/him?
Do you trust him?
and back to...WHOM do you trust?

[jejones]

OK...it might be better to turn questions into declarative statements, because the nominative/accusative distinction is the same. Which looks right, "You trust he" or "You trust him"? The latter (I hope :), so it's "Whom do you trust?"

[NCLaw441]

Turn the sentence around a bit, and it becomes clear:
Do you trust HE?
vs.
Do you trust HIM?

[rwfromkansas]

Turn the question into a statement. That is what I do and it is a lot easier than just leaving things as questions.

"Who/whom do you trust?"

=You do trust he. (this is obviously incorrect we can see)
=You do trust him. (him is the direct object in this sentence, necessitating the usage of the objective form of who/whom)
=You do trust whom.

Final answer:

"Whom do you trust?"