The dilemma of Who/Whom

I know this blog post is almost late, but I am still humbled by the solution to the Who/Whom dilemma. In all of my years of elementary, middle, highschool, and college, I never learned how to differentiate between Who and Whom. I've recently learned that in order to distinguish which one you must use, it is necessary to see if you can replace Who/Whom with "he" or "him". If "he" is the appropriate replacement, then one would use "Who". Conversely, if "him" is the appropriate replacement, then one would use "Whom". Such a useful grammar tool!