Make it to the bottom of the Citadel's main elevator shaft in one piece.
Contain the Citadel core.
Contain the Citadel core without killing any stalkers.
Car Crusher Achievement
Use the cars to squash 15 antlions in Episode One.
Elevator Action Achievement
Survive long enough to get on the parking garage elevator.
Live Bait Achievement
This Video Shows you the basics, simply move around the area long enough for Alyx to make 30 enemiy kills with the sniper rifle.
Help Alyx snipe 30 enemies in Episode One.
Destroy the gunship in the hospital attic.
Kill five enemies with the same energy ball.
Think Fast! Achievement
Kill an Elite Soldier with his own energy ball.
Use flares to light 15 zombies on fire.
Citizen Escort Achievement
Don't let any citizens die when escorting them to the escape train.
Escape From City 17 Achievement
Escape City 17 with Alyx.
The One Free Bullet Achievement
Finish the game firing exactly one bullet. Grenade, crowbar, rocket, and Gravity Gun kills are okay!
Basics is, during the beginning of the game you will find your first weapon the Shotgun. You will Need this in order to exit the locked room and the padlock is on the otherside of the gate and you have to shoot it off. Once this is done, that will be your first bullet fired. You can no longer use any Gun for the rest of the game, save for the Gravity Gun, rocket, crowbar and granade.
During Act : "Low Life"
The Following Video Is A Basic Walkthrough To Get Past The Antlion Gaurdian.
There are a few videos out there on a glitch you can use, this shows the normal way to take'em down.