I had huge problems with the high school section, because I didn't know where to go.
Died so many times... One of the annoying aspects of the game is that if two of the enemies get on you at once, you're just about screwed. Makes it really difficult.
But for me, once I got to the safe point in the high school, it became much easier. Realize that it is a safe spot. Your character will recharge his health when he is there. It's also pretty easy to locate when doing camera runs as there is a huge arrow on a board pointing to it.
To pass the camera section, what I did is do it in two parts. The first part I took two of the pictures (I didn't do the parking lot one in this run). I then returned to the safe house and saved. I then made the 3rd picture its own run. It helps if you press the right D-Pad to take the picture, it's faster than navigating through the phone as monsters are still after you and the game does not pause in nightmare mode unless you press the Home button.
After the high school nightmare, I did give the next nightmare an honest try. I tried it like 4 times. I then broke and went to GameFAQ's.
Those sections scare the hell out of me. In real life, all of my nightmares are of me getting chased with no way of fighting back.
Another hint: Turn off your flashlight.
I also completely gave up on trying to be sneaky or to hide. In every nightmare, I always end up running like a bat out of hell. Usually into the creatures