Who or Whom?
Some say that ‘whom’ is going out of fashion and that you should not bother about it at all. This sounds too easy don’t you think? So, in the meantime …
If you could replace the word in question with he/she/they/I - it’s who.
If you’d say him/her/them/me - it’s whom.
It seems to be working for me but I’m sure that like all good rules there will be an exception that will cause me grief.