Finding a scary movie idea means looking into the soul of culture: understanding how and why people fear, then invoking these fears with sounds or images. But people fear many things. Because of this, the type of horror you make depends on your fear as well. Choose a movie idea that truly frightens you, perhaps so much so that you have trouble sleeping while researching.
Folklore illustrates the timelessness of certain scary tales. By repetitious telling, these stories become part of the collective unconscious, and more readily ignite fear in fans. Once you find a folklore tale that scares you, look into the cause of the story's ability to incite fear. For example, the werewolf legend has played a part in many cultures, and maintains its ability to frighten.
Relate the Period
Much like world history, horror history is marked with thematic periods. Horror movies from each period display one major type of monster, effect or horror location. For example, when “talkies” first hit the cinematic screen, the mad scientist was a common villain. The '50s made the mutant famous. Contemporary horror (2000s) often explores global pandemics and disease.
To find horror movie ideas, learn how world events contribute to horror movies. Although you don’t want to copy this pattern exactly, it can illuminate the relationship between events and the subsequent fear.
Utilize Viewers’ Surroundings
Use the viewer’s natural surroundings to create your movie. If you know that your audience will view your movie in quiet living rooms, then create a movie that plays on the horror of silence; for example, a movie where the hero (and ultimately the audience) is deaf. If you plan on showing your movie in a drive-in, then create a horror where monsters hide outside of the hero’s car.
Some might consider creating a movie for your viewer as backwards, but it is not dissimilar to painting a portrait to go on your wall.
Horror and Anger
Some horror movies (grind-house cinema style or B movies) do not use fear as their main audience reaction, but instead anger. Although these movies make effective use of gore, they do not create in the audience the same emotional reaction. While fear produces an overestimation of risk in the person who is afraid, anger does the opposite, creating an underestimation of risk. Therefore, a viewer made to feel angry won't find his surroundings very scary. Additionally, an attempt to make a viewer angry before making him scared ends with the fear not quite setting in.
Conversely, a movie director can use anger-causing cinema to alleviate the fear of the audience, resolving early fear before the end of the film.