Stares
The next time you are in a public place, take notice of how many people are actually looking into the eyes of other people. Even if they are talking to someone, chances are they are looking away, here and there, and at most, merely glancing at their companion's eyes. In our culture, looking into someone's eyes for longer than a few moments means one of two things: intimacy or challenge.
In a haunted house, good eye contact is more effective than a loud scream. Facial expression is important, because it telegraphs the intent of your stare, so it is best to keep your face perfectly neutral and let them draw their own conclusions.
Often the victim will have trouble maintaining eye contact with you, yet they will also find it hard to look away. Much like a snake hypnotizing a bird, a victim will feel physically trapped by your gaze, and this only amplifies their feelings of helplessness.
There is something of a gender difference in reactions to this. A man staring at a woman is more likely to be considered threatening than if a woman is staring at a man. In fact, the woman staring at a man may find the man interprets this to be an invitation. On the other hand, a man staring into the eyes of another man is much more likely to cause a challenge response.
But like a recipe, this one ingredient is best when mixed in with others. Combined with Stillness and the right kind of Movement, Staring is a powerful amplifier of fear.
Click below for an example description from the Haunted Theater.