Take a shot for every time you miss an attack when a Monster backs away.
Take two if it attacks afterwards.
For Wii U users: Take two shots every time you try to Z-Target a monster because you've played so much Zelda. For 3DS users: two shots every time you try to L-Target a monster because you've played so much Ocarina of Time 3D.
Also for 3DS users take a shot for everytime you press L to aim your bowgun because you've been playing Resident Evil: Revelations.
Take a shot every time you get violently interrupted when trying to cook steak.
Take a shot every time the Deviljho shows up randomly. Or rather, don't, because you'll need to be sober to escape that thing, let alone fight it.
Take two shots if the Deviljho Slendermans you. That is, if this unlikely scenario happens to you: you walk up to an area boundary right as the Deviljho at your destination decides to move to the area you're in, and the Deviljho just APPEARS out of nowhere inches from your face.
And take three if you see a SAVAGE Deviljho. Don't even bother being sober, just run!
Take a shot every time you curse the Random Number God for not giving that item you need just one more of.
As a matter of fact, take a shot for every Rathian/Rathalos Plate you DO get. Those items are BITCHES to find.
And one for every Diablos Medulla. Dear God.
Take an extra shot if you cut off a monster's tail, carve it, and don't get the tail as an item.
Take two shots every time you get more items than you should from a monster. This counts for carving (such as getting 3 Rathalos Wings from one Rathalos or getting multiple Deviljho Tails from one severed tail) and for rare commodities obtained when freehunting (e.g. getting 3 Zinogre Heads from one Zinogre.)
Take a shot every time you accidentally hit yourself with a Felvine Bomb.
Toast your victory with a glass of expensive champagne whenever you kill one of these monsters for the first time: Ceadeus (repelling counts), the Jhen Mohran (repelling counts), the Ivory Lagiacrus, the Deviljho, Dire Miralis, Alatreon.