In my own humble opinion. If you know what's going to happen it's not scary.
One of the main things that makes horror scary is because it's mysterious. You don't know what's happening or what's going to happen. Everything is tense because you don't understand what you're dealing with.
If someone goes berserk that's scary. If you know that it's Steve and he's gone psychotic because he's drunk, his wife has left him, and he's a dick, Steve isn't as scary. Going down a dark hallway is scary. Knowing what's hiding in the corner rubbing it's hand with glee is not scary.
That moment in horror when the protagonist realizes what's happening, when he knows what's gone wrong, when he knows the monster is behind him with a bottle of lube is often THE scariest scene in the work. However after that things can't ever be truly scary again. It can be tense, but only in the sense of action. The mystery is gone.
In your regular zombie movie I doubt most people were left scared, or at least the second time. You don't think "oh no the dead are walking", you think "shoot that ************ in the head". If you understand what's threatening you, you can rationalize it. If you open a door and there's a 20 foot cockroach you can think "hey at least it isn't 40 foot", if it's 40 foot you can think "at least it isn't 60 foot" and so on. You can't rationalize what you don't understand.
As such even though it's still hard to make horror, the base rule I guess would be not to tell the audience everything and leave them to stew.
Now I will like to be proven wrong. Laugh at me and so forth. Throw several books at me. Show that I have made a fatal flaw in my reasoning. Show me something which was scary because you knew how the character was screwed or was even made scarier.
P.S
Sequels to horrors are almost always going to suck. So as reusing monsters. The elder gods in H.P Lovecraft's novels were scary because they were incomprehensible. Silent Hill and Fatal Frame are exceptions, because the threat is inscrutable. If there's some mystic kid running those villages he's been wisely kept out of sight.
One of the main things that makes horror scary is because it's mysterious. You don't know what's happening or what's going to happen. Everything is tense because you don't understand what you're dealing with.
If someone goes berserk that's scary. If you know that it's Steve and he's gone psychotic because he's drunk, his wife has left him, and he's a dick, Steve isn't as scary. Going down a dark hallway is scary. Knowing what's hiding in the corner rubbing it's hand with glee is not scary.
That moment in horror when the protagonist realizes what's happening, when he knows what's gone wrong, when he knows the monster is behind him with a bottle of lube is often THE scariest scene in the work. However after that things can't ever be truly scary again. It can be tense, but only in the sense of action. The mystery is gone.
In your regular zombie movie I doubt most people were left scared, or at least the second time. You don't think "oh no the dead are walking", you think "shoot that ************ in the head". If you understand what's threatening you, you can rationalize it. If you open a door and there's a 20 foot cockroach you can think "hey at least it isn't 40 foot", if it's 40 foot you can think "at least it isn't 60 foot" and so on. You can't rationalize what you don't understand.
As such even though it's still hard to make horror, the base rule I guess would be not to tell the audience everything and leave them to stew.
Now I will like to be proven wrong. Laugh at me and so forth. Throw several books at me. Show that I have made a fatal flaw in my reasoning. Show me something which was scary because you knew how the character was screwed or was even made scarier.
P.S
Sequels to horrors are almost always going to suck. So as reusing monsters. The elder gods in H.P Lovecraft's novels were scary because they were incomprehensible. Silent Hill and Fatal Frame are exceptions, because the threat is inscrutable. If there's some mystic kid running those villages he's been wisely kept out of sight.