More Ideas:
It should be from a different era. Like, the fifties or thirties, when mental hospitals used electroshock therapy. Creepy stuff.
Each chapter should be based off of a song. And while you're writing, listen to a band's album. It'll help get you in the mood.
Really develop character personalities.
Have some flashbacks.
There's some more ideas I have
Also: for my character (this part isn't true) I've had really bad experiences and a lot of mental scarring so to feel safe I act like a little girl.
Author's response
Yes Flashbacks'll be in there.
I'll develop my character's personality a lot too.