While there are obvious moral choices in the game (where both decisions are clear), there are plenty of subtle moral choices that will determine which ending (just two) you get at the end. When selecting an action, the game world will temporarily flicker with a rust-ochre color (and you will hear faint murmuring) if you made a moral choice (good or bad).
While playing the Armory level and after meeting Andrew the Blacksmith, you have access to ammo and two guns at his shack. Pick them up and trade them at the weapon shop for a "Duplet" to earn a 100-200 bullets profit, giving you enough money to buy the best weapons available, a suit, and load up on ammo.
Note: This procedure requires editing a game file; creating a backup copy of the file before proceeding is recommended. With a text editor, edit the "user.cfg" file in the game directory. Change the following lines to activate the corresponding cheat:
CHEAT FUNCTION/ORIGINAL VALUE - NEW VALUE (God mode) g_global_god off g_god off - g_global_god on g_god on (Unlimited ammunition) g_unlimitedammo off - g_unlimitedammo on
There is an objective in "Outpost" concerning an S.O.S. message from "Defense". Enter the first Nazi controlled building where a Demon snatches a fleeing Nazi and fight through the area until reaching the upper level of that building. Once there, find a hallway with three tripwire mines and two Demons. Get past the mines and check the right room at the end of the corridor to find a ramp that gives access to the rooftop. You will find a corpse with a Kalashnikov on the rooftop. The communications apparatus for the achievement is located in the corner of the rooftop.
Besides purchasing the Sneaking Suit at Armory Station, you can get a pair of nightvision goggles at Front Lines. When in control of Artyom, turn around and follow the train tracks. The nightvision goggles will be in a red breaker box guarded by two soldiers.
Before getting into the train car at Armory Station, you can buy a Stealth Suit for 100 military cartridges from the vendor across from the Ammo Exchange. There is a vendor next to that one that sells a damage-decreasing Armor Suit. Both suits can be worn simultaneously. A similar Armor Suit is also sold by a vendor next to the Ammo Exchange in Polis.
-When in the Library, the two rangers will announce the titles of numerous books. One of them is "Roadside Picnic" (1977) by the Strugatsky brothers, which was the book that Andrei Tarkovsky's 1979 movie "STALKER" was based on, which then was the inspiration behind S.T.A.L.K.E.R. Shadow Of Chernobyl.
-The first person you can speak to resembles a "loner" Stalker and says "Take it easy bro!"