Here are the rules:

Take a drink whenever: Someone says, "McClane" or "Nakatomi". There's a reference to Christmas. McClane talks about being a cop. Someone dies.

whenever: Finish your beer when McClane says, "Yippee ki yay, motherfucker!"

when McClane says, "Yippee ki yay, motherfucker!" Waterfall while Gruber falls to his death.

If you wanna kick it into full gear, tack on these additional rules: