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

Off the Boat (5 points): Complete the first mission. 
One Hundred and Eighty (10 points): In a darts game score 180 with 3 darts. 
Pool Shark (10 points): Beat a friend at pool. 
King of QUB3D (15 points): Beat the High Score in QUB3D 
Finish Him (15 points): Complete 10 melee counters in 4 minutes 
Genetically Superior (25 points): Come first in 20 singleplayer street races. 
Wheelie Rider (30 points): Do a wheelie lasting at least 500 feet on a 
motorbike. 
Gobble Gobble (10 points): Score 3 strikes in a row, a turkey, in 10-pin 
bowling. 
Driving Mr. Bellic (10 points): Unlock the special ability of taxi. 
Rolled Over (30 points): Do 5 car rolls in a row from one crash. 
Walk Free (50 points): Lose a 4 star wanted rating by outrunning the cops. 
Courier Service (10 points): Complete all 10 package delivery jobs. 
Retail Therapy (10 points): Unlock the special ability of buying guns from a 
friend. 
Chain Reaction (20 points): You must blow up 10 vehicles in 10 seconds. 
One Man Army (40 points): Survive 5 minutes on 6 star wanted level. 
Lowest Point (5 points): Complete mission "Roman's Sorrow". 
Over Fulfilled (10 points): Complete all 10 Exotic Export orders. 
Manhunt (15 points): Complete the most wanted side missions from the police 
computer. 
Cleaned the Mean Streets (20 points): Capture 20 criminals through the police 
computer. 
Fed The Fish (5 points): Complete the mission "Uncle Vlad". 
It'll Cost Ya (5 points): Complete a taxi ride without skipping from one 
island to another. 
Sightseer (5 points): Fly on all helicopter tours of Liberty City. 
Warm Coffee (5 points): Successfully date a girl to be invited into her house. 

That's How We Roll! (10 points): Unlock the special ability of helicopter. 
Half Million (55 points): Reach a balance of $500,000. 
Impossible Trinity (10 points): Complete mission "Museum Piece". 
Full Exploration (20 points): Unlock all the islands. 
You Got The Message (20 points): Deliver all 30 cars ordered through text 
message. 
Dare Devil (30 points): Complete 100% of the unique stunt jumps. 
Assassin's Greed (20 points): Complete all 9 assassin missions. 
Endangered Species (50 points): Collect every hidden package in the game. 
Under the Radar (40 points): Fly underneath the main bridges in the game that 
cross water with a helicopter. 
Dial B For Bomb (10 points): Unlock the special ability of phoning for a bomb 
to be placed. 
Gracefully Taken (10 points): Complete mission "I'll Take Her". 
Liberty City (5) (20 points): After meeting all possible friends, the ones 
left alive all like you above 90%. 
No More Strangers (5 points): Meet all random characters. 
That Special Someone (10 points): Complete mission "That Special Someone". 
You Won! (60 points): Complete the final mission. 
Liberty City Minute (30 points): Complete the story missions in less than 30 
hours.