I started off like everyone else does, slogging but having a compulsion to put words on paper. I didn't write or read horror or fantasy, other than children's fantasy, until I was in my teens.
I cannot say how strongly I object to people using other people's writing as research. Research is non-fiction, especially for horror, fantasy, science fiction. Do not take your research from other people's fiction. Just don't.
My characters surprise me constantly. My characters are like my friends - I can give them advice, but they don't have to take it. If your characters are real, then they surprise you, just like real people.
Most of the monsters... are based on some sort of mythology. Every culture and even some geographical areas have monsters and mythology that is their own.
I think that my vampires in general were influenced by my being allowed to watch the Hammer vampire films. Vampire Circus, also shown as Circus of Fear, was one of those movies.
I've lost track of the number of people who want to be writers but never actually write anything. Talking about writing, dreaming about writing, can be very fun, but it won't get a book written. You've got to write.