When I was in my early teens my friend, Mandy, and I had a weekend ritual. Friday night was horror movie night.
Mandy had the best house for horror movie watching. Her parents had a thing for weather-beaten farm antiques. Rusty scythes and pickaxes hung from the wall like a bad movie set. They also had one of those second garage freezers stockpiled with frozen pizzas and tv dinners. Put all that together with a pull out sofabed in front of the tv, and her place was heaven as far as my thirteen year-old self was concerned.
We would scour the video stores for titles. We went through what the big chain store had to offer quickly-- big name slasher film series and a few mainstream flops. The little local independents had better titles--everything from the campy B-movies(I was thirteen when I first fell in love with Bruce Campbell) to Italian art house horror.
I learned a lot from those late night vhs double features. Scene structure has to be tight in a horror story, more so than in other genre, for it work effectively. Don't be afraid to start big and end bigger. Make your protagonist relatable. If I don't care about them, I'll spend the whole time rooting for the killer.
Sometimes it's inevitable. Take Pinhead from Hellraiser, my favorite movie monster.
He's not even the real bad guy in the story. Frank is, but very few people remember him at all. Frank is a one-note character, all bad. He's necessary, but not interesting.
But, Pinhead? He's got pizzaz. He's not strictly a villain. He comes from another place where the code is different. He's even reasonable, in his own freaky way. Sure, he'll "tear your soul apart", but only cause you asked him to. Don't want "your suffering to be legendary even in hell"? Well then, don't open the freakin' box. Simple as that.