Alan Wake

Considering the way that Alan Wake plays out there is absolutely no reason for you to ever play on the Hard difficulty. Difficulty achievements stack, meaning you only need to beat the game twice - once on Normal or Hard unlocks Nightmare and then play through Nightmare.

Playing through the game on the Normal difficulty will allow you to get most of the other achievements in at least one run, including the manuscript and other collectible achievements. Go back, play any Episode you need to get achievements you've missed and then move on to Nightmare. Skip over Hard entirely since it's somewhat redundant.

The only difference difficulty level makes is how hard it is to defeat the Taken. On Hard enemies have about 50% more health and on Nightmare they have around twice the health they do on Normal. There are also 15 new manuscript pages to collect on Nightmare but that's for another guide.

MINOR SPOILERS AHEAD!

Not difficult at all. Only certain parts are difficult but only because they require you to think on how to strategically beat the enemies.

Some tips:
-For normal enemies use the revolver.

-For the huge enemies that are like 7 ft tall use high powered guns like the hunting rifle or shotguns.

-Learn how to use the dodge move (LB+LS), it saved my neck many, many times.

-When your health goes down and there are several enemies do not hesitate to throw down a flare, that will keep enemies away.

-For the poltergeist (movable objects) always try to get behind cover, even simple poles and even boxes will do the job as the poltergeist won't hit you.

-If the birds keep rushing you and you're not able to hit them with your flashlight, it's a good technique to hold up a flare in your hand.

-If you are low on health and low on ammo and items, look for the nearest source of light. Throw down a flare and make haste towards the nearest light.

I'd recommend you do this on your first play through as it's not that hard. I even managed to accumulate 73 manuscripts and 73 thermos during my first playthrough in hard difficulty.

This chievo stacks, so unless you're a bit of a masochist, better to complete the game on Normal difficulty first, then once complete and Nightmare mode is unlocked, complete it on Nightmare. When you complete Nightmare mode, it'll unlock this chievo as well...

And Nightmare mode really isn't that much harder than Normal difficulty - the biggest difference seems to be how much darkness protects the taken, and how much ammo you need to use to take a Taken down...