One tried-and-true method is to control what an audience knows about the story before experiencing the storytelling process so that you can shock them. Within the context of the story itself (as opposed to marketing or word-of-mouth), an author can prepare the audience by establishing certain givens, then purposefully break the storyform (destroy the givens) to shock or jar the audience. This hits the audience at a Preconscious level by soliciting an instantaneous, knee-jerk reaction. This type of propaganda is the most specific and immediately jarring on its audience. Two films that employed this technique to great effect are Psycho and The Crying Game.
Psycho broke the storyform to impact the audience’s preconscious by killing the main character twenty minutes or so into the film (the “real” story about the Bates family then takes over). The shock value was enhanced through marketing by having the main character played by big box office draw Janet Leigh (a good storytelling choice at the time) and the marketing gimmick that no one would be allowed into the movie after the first five or ten minutes. This “gimmick” was actually essential for the propaganda to be effective. It takes time for an audience to identify on a personal level with a main character. Coming in late to the film would not allow enough time for the audience member to identify with Janet Leigh’s character and her death would have little to no impact.
The Crying Game used a slightly different process to achieve a similar impact. The first twenty minutes or so of the film are used to establish a bias to the main character’s (and audience’s) view of reality. The “girlfriend” is clearly established except for one important fact. That “fact,” because it is not explicitly denoted, is supplied by the mind of the main character (and the minds of the audience members). By taking such a long time to prep the audience, it comes as a shock when we (both main character and audience) find out that she is a he.
From the Dramatica Theory Book