Aliens Colonial Marines

This mission starts out in a Weylan-Yutani research facility. Go through a room or two until you reach the locker room. The small office on the right has an Audio Log next to a piece of armor.


Walk around the lab's halls until you reach the outside area. Several W-Y PMCs will be fighting Xenos. The very first PMC will have a ton of armor with a heavy duty gun. Stay behind cover and use explosives if need be.


Follow O'Neal further out. The first building out of the area contains quite a bit of ammo - you might want to stock up. Keep fighting until you reach two more buildings. The first building has a bit more ammo and armor, but the second building nearby will have a set of Dog Tags inside on a yellow crate.


Fight your way through the hordes until you reach a derelict ship. More PMCs will be inside, so stay on your toes. The first building on the right contains another Audio Log. This should be the last one in the game, unlocking the I Heard THAT achievement.

Head to the elevator at the other end of this area. You'll have to fight quite a few soldiers on the way, but no Xenos. Further ahead is a familiar face, if you've seen the original “Alien” movie. Up the set of stairs is a set of Dog Tags, behind the giant fossilized man sitting in the chair. Grab them and fight the Y-T PMCs until you exit the ship.


Outside will be more PMCs and Xenos. Fight them all off as you inch your way into the W-Y research facility to rescue the captive marine. Before going too far, look for a green truck on the left side of the road. Follow the road up to a set of Dog Tags on a crate behind a second truck.


The captured marine isn't far ahead. Reach the area he's being held at, and kill the PMCs surrounding him to complete the mission.

Courtesy of IGN.