Ghost was telling the new recruits about how to be serious and how to use guns and telling them about everyone until it came to you, you always kept your head tilted down and looked forward making you look psychotic so Ghost says

Ghost:”how do you make a character quickly look psychotic it’s easy just use the Kubrick stare all it requires is 2 steps 1.tilt the head down slightly 2.stare forward though the eyebrows it’s a technique.”