Ghost (achievement)

Ghost is an achievement/trophy in Deus Ex: Human Revolution. It is earned by getting through a hostile area without raising any alarms.

"You made it through an entire hostile area without so much as a squeak."

Overview
To get this achievement you need to get through a hostile ocupied area without setting of any alarms. You are allowed to kill the guards as long as they don't turn hostile towards you.

Strategy
This is one of the easiest achievements to get, although it doesnt sound like that.

In the first mission (when Adam is augmented) choose in the helicopter for a non-lethal and then the tranquilizer rifle. As the helicopter lands and you get down on the floor the first guard is just around the corner. Take him down with a silent takedown. A bit further are 3 more guards. Wait a few seconds to analyse their patrols and then start taking them out. First the one at the far end (next to the door). The second one should be the one patroling in the middle, shoot him also with the rifle. Then crouch sneak to the one who is standing the closest to you and take him out with a silent takedown. Then enter your objective building. The achievement pops up.