What makes something scary

[skypeskype]

Here is MY idea for something scary:

Spawing a monster when picking up a key, or resolving a puzzle won't scarre the player at all becasue:
1. You expect it.
2. You are happy for doing that hard puzzle so the monster won't scare you as much

The most common rooms in wich you expect to get scared are storages and cellars. So you WONT do it in there maybe only if you think of a very very clever scare. In those rooms, maybe build up lots of scary atmosphere with scary corridors, posible hiding spots and music. The player will feel relieved when leaving this rooms, so they wont expect getting scared so THATS when you hit him.