To complete this game on Nightmare is not too much of a challenge, once you've worked out a few things.
As you'll have already done one run through, you'll know how the game works and hopefully done all but the Nightmare Scripts in the collectables.
The most important thing to learn how to do is the Dodge (Tap LB and move) this will get you out of most situations.
Where possible, just run for the lights (Checkpoints). Once you've got it you can scout the area without too much difficulty. I used the lights to kill off any taken by tempting them into the light.
For flying objects, just put something between the object and you, like a post or box and then they hardly ever hit you, giving you time to let your torch recharge.
Flares are really useful and I collected all Ammo Crates and any other Ammo/Supplies I could find, even on Nightmare. Dropping a flare can sometimes get you to a Safe Haven without using any Ammo.
Talking of Ammo ... the most important thing I found is this .. At the start of each Episode you start off with Nothing, so use it all up at the end of each Chapter.
Here is an excellent link that tells you about all the collectables.http://www.xbox360achievements.org/forum/showthread.php?t=23...
this was written by Tyger7.
I didn't find any problem area's, even the ones mentioned above were not too bad. Enjoy