Ahhhh... Yeah.
Darkness, skeletons, blood... not scary.
Good lighting - Make the player see what you want him to see, and leave some darkness around, but not pitch black.
Sounds - Spooky background music and sudden triggered sounds.
Objects - Characters and other objects that seem to appear suddenly and from nowhere.
Confusion - Keeping the player lost or disoriented with paths that go nowhere or lead back onto themselves.
I'm sure others can think of more...
Best.
I'm sorry, my answers are limited. You must ask the right question.