An Example from The Haunted Theater
Alien Motion
When you are very still, or when you move slowly, people will find it hard to look away from you. For example, as a group of victims approaches you, after a period of stillness, slowly turn your head to face them. In the proper environment, this will produce chills and fear reactions that are much deeper than a mere startle reflex. In addition, while they are preoccupied with you, a fellow ghoul can quietly appear behind them, make a small sound, and wait for the resulting screams as those in the back of the group realize they are not alone. The resulting domino effect is much more powerful because you have built up suspense and primed them for a release.
At the other extreme, a quick "here and gone" can also put your victims on edge. Pop your head out from an unexpected place, and before they can quite figure out what they have just seen, disappear again. Do this several times from different, unexpected locations, and you will have them trying to look everywhere at once. Combine this with some of the other techniques discussed, and you can truly make their heads spin.
Another technique related to "here and gone" is the disappearing act. Allow your victims to see you and approach. Arrange for a distraction that makes them turn their heads away from you for just a moment. In that moment, duck into a preplanned hidy-hole before they turn around. When they turn back around, your sudden disappearance will be just as distressing as a sudden appearance. You can milk this further by arranging a series of hidden passages throughout the haunted house that will allow you to get ahead of them several times. After the third time, instead of disappearing, have another ghoul join you, and slowly advance on them. The result will have much more impact because of the priming you did.