WASD moves, hold down shift or right mouse button to sneak. You can't move across furniture tiles while sneaking.
When sneaking, approach an unaware enemy until the "CLICK NOW 4 MURDER" prompt appears on top of them to stealth-kill them. Click when not sneaking to shoot while you aren't out of ammo, but this makes noise that makes nearby enemies become alerted and come running. Press B to drop a proximity bomb when you have one, but don't be nearby when it arms!
Press F when in sight of a hostage to order the hostage to come to your current location. You can call hostages that you have previously ordered out of sight within a set radius. Enemies will kill hostages that are trying to escape on sight. Lead hostages to the green rescue area while there are still enemies alive to free them and get a score bonus.
Press L to toggle a laser sight to help you aim. Press forward-slash to toggle sound.
Click here for sound credits.