Decide on the purpose of a shocking depiction or description in your work. Consider what you wish to accomplish by shocking your audience. Ask yourself if you want to educate them or change their opinion, and why. Consider if shock value is the only way to achieve your desired results or if you can grab your audience's attention another way.
Determine what kind of reaction you to want to elicit from your audience, whether one of outrage, disgust, hopelessness or fear. Decide which reaction best relates to the message or purpose of your text or visual. Graphic pictures of lung cancer and blackened teeth on the front of cigarette cases are examples of shock rhetoric intended to disgust smokers into quitting.
Choose what kind of shock value you want to utilize in your work, whether it be graphic violence or a taboo topic, such as cannibalism. Consider how explicitly or subtly you wish to present the topic. Sometimes subtlety can have a powerful effect on viewers or readers. For example, in the Italian Holocaust film "Life is Beautiful," in contrast to Spielberg's "Schindler's List," director Benigni refrains from showing any graphic images of suffering in a concentration camp, until one horrifying moment where the protagonist stumbles upon a dark, vaguely defined pile of bodies, too shadowy to see clearly but effectively gruesome and shocking nonetheless. Subtlety can be shocking too.
Compel your readers to become invested in your story before you shock them. If you are writing a story, develop strong characters with depth with which readers cann sympathize and get to know. Then readers will be more likely to stick out the shocking scenes, such as in Louis de Bernieries' "Senor Vivo and the Coca Lord," where the author has the beloved girlfriend of the main character horrifically chopped to bits in order to represent the utter depravity of the Columbian drug trade. This scene is so heart-wrenching because readers have come to love and enjoy watching the relationship develop between the two lovers.
Weigh the ethics of your decision to utilize shock value. Consider if your visual or text is unnecessarily offensive or disrespectful to certain groups of people, such as a religious or ethnic group. If you are using depictions or descriptions of real people, consider the ethics of sacrificing their possible dignity for the sake of making a point.