There are 12 achievements worth a total of 200 points
Beat 5 advanced chambers
Dissolve a turret.
Beat 10 advanced chambers
Knock a turret over with a security camera.
Win a gold metal on a challenge map.
Trap yourself in a test chamber so that GLaDOS has to help you continue.
Find the chicken's test results.
Cause a rocket sentry to destroy its own rocket when the rocket has been redirected back towards it.
Complete the game without ever taking a bullet.
Once you have control of both portals, only enter the orange portal.
Beat all advanced chambers
Find all the Rat Man dens.