Take a shot whenever a gun is fired in a cutscene.
Take a shot whenever someone is disarmed in a cutscene.
Take a drink when Nate has to climb something.
Take two drinks if the object he's climbing on starts to fall apart or exposes him to unforeseen danger.
Take a drink whenever a main character in a cutscene walks off what should have been a fatal or paralyzing injury with just scratches.
Take a drink when Nate is in peril.
Take two drinks if Nate has to save a partner from peril.
Start chugging if Nate does the above while he is in peril.
Take a drink every time a cutscene plays.
Take a drink every time Nate says "crap".
Take two drinks every time someone says "shit".
Take three drinks every time he says "Nonononono!" You're guaranteed a trip to the hospital.
Take a drink whenever Nate gets out his journal.
Take two drinks when Nate uses the journal to solve a piece of the mystery surrounding the game's treasure.
Take a drink the first time you open the journal for a puzzle. Every time you need to open the journal again on the same puzzle, take the previous number of drinks + 1. If you have to look at the journal because you thought an incorrect solution was correct, double the previous amount of drinks. If you give up and need to use the internet, take a shot for every minute you've been playing during that session.
Take a drink when Nate has to solve a puzzle.
Take a drink whenever someone's ass is mentioned or complemented. Take two if it's Chloe's.
Take a drink whenever the basic laws physics do not apply to enemy mooks; this should happen often when using BFG against them.