Firstly, lets get an obvious truth out of the way: few people know and few people care nowadays. The word who seems to be universally acceptable, but I'm not here to acquiesce to current trends.

First we need to know about subjects and objects in sentences. In the sentence "I am going to beat him to death", I am the subject, and he, most definitely, is the object.

In this case the subject is "who" and the object is "whom". You could correctly ask, "Who beat whom to death".

Who is always the object of a sentence, while whom is the subject.

A simple trick to remember is to think of whether you would expect the answer to any question to be "he" or "him", and the final letter of "him" gives the clue: "Who loves ya baby?"; the answer is " He" loves ya, which doesn't end in "m" and therefore Kojak was right to ask the question as he did.

Conversely, "Paul Dean is a man whom I admire greatly" prompts the question "Whom do I admire?" and the answer is "Him", which ends in "m" and therefore points you towards "Whom" which is correct.

Dead simple really.