Use of foreshadowing is key. Drop little hints in the preview about something bad that might happen. For instance, a character might mention a local legend that seems to be coming to life.
One reason could be the unknown elements. In a mysterious horror story, not knowing what's lurking in the shadows or what will happen next creates a sense of unease. For example, in many classic horror stories, there are strange noises or movements that are left unexplained for a while, which builds tension.
Previews for Toy Story 4 usually last around 5 to 10 minutes. However, this can differ based on the cinema and any special promotions or sneak peeks included.
You can usually find story previews on the official websites of authors or publishers. Sometimes, they are also available on online bookstores or reading platforms.
The length of the previews before Toy Story 4 can vary. Sometimes they might be around 10-15 minutes, but it really depends on the theater and the specific screening.