Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Ice Station Santa (20 points): Complete Episode 1 - Ice Station Santa.
Moai Better Blues (20 points): Complete Episode 2 - Moai Better Blues.
Night of the Raving Dead (20 points): Complete Episode 3 - Night of the Raving Dead.
Chariots of the Dogs (20 points): Complete Episode 4 - Chariots of the Dogs.
What's New, Beelzebub? (20 points): Complete Episode 5 - What's New, Beelzebub?
Went Beyond Time & Space! (30 points): Complete Sam & Max Beyond Time and Space.
Did Someone Say Birthday? (10 points): Celebrate the Bug's birthday before his family arrives.
Sandwich Seller (10 points): Offer the granite sandwich to everyone on the island.
Monster Master (10 points): Try every possible body part in the monster.
AI Interrogator (10 points): Choose every dialog choice with each AI personality.
Office Snoop (10 points): Spy on Satan berating the staff each time the efficiency drops.
DeSoto Dominator (20 points): Win every upgrade for your car, and claim the Uber Mystery Upgrade.