If you've never seen the 1999 American Movie documentary, you really need to. It's an extraordinary doc about 2 guys in Wisconsin (Milwaukee?) who set out to make a low-budget horror despite all odds.
What's so fascinating about this is how hard this guy works yet seems to get nowhere. He's a smart and knowledgable guy but his drinking and shortsightedness (like hiring his friends instead of experienced crew members) get in his way constantly, as he tries to make the ultimate American Movie.
The master of suspense was of course, Alfred Hitchcock. Too bad he was such a womanizing creep. Anyway, a good horror, like The Strangers picture above, utilizes suspense by keeping viewers and the characters in a state of prolonged anxiety and dread.
"You are traveling through another dimension, a dimension not only of sight and sound but of mind. A journey into a wondrous land of imagination. Next stop, the Twilight Zone!" The opening credits to The Twilight Zone read by Rod Sterling.