Oh boy, horror. Horror is rather a broad genre; psychological horror, body horror/gore, thriller, paranormal, 'disturbing' and different kinds of 'creepy' horrors. I'm sure you know what you're going for in what kind of horror, yes? Won't dawdle on them. The things I keep in mind is don't even try to scare the reader, as if you are trying to, but comes off as a turn off. You don't even need to think "how to scare them?" / "how do I make them feel..." while writing it... eventually, it'll come naturally. Your characters' fears, your readers' fears, and your fears... Have the readers get drawn into your characters' head, as if they are there in the settings. Speaking of horror and seeing the recommendations.. Rubber (2010) film, strange/disturbing and a dip of gore was done. I still shake my head whenever I remember that movie..
my advice (being someone who continually writes horror) is to use what scares you, or a phobia. that i find helps create a good catalyst for the main driving point of the plot, and you can use a mix of the stereotypical horror things such as dark woods, half ton of blood, etc, etc. and mix it with some more unusual elements (like in one of mine, a snow-fox)
