Some placements might have been changing depending on particular save, don’t worry and look around the given place.
You basically need to finish the game three times in order to achieve everything. I recommend you to finish most of achievements in a „good/solo“ run for "The past is always with us". You'll eventually get rest of them when going for "duo" run and "Continue to live??" achievement. Finally, replay the game for bad ending and "Repose".

At the very beginning of the game, as soon as you come out of forest to the road, there is a cutscene. After that, turn back and go the same way you’ve come. After several steps you start hearing trumpeting from the sky and the further you go, the louder it is.
cutscene with a car

In the reminiscence of the hospital, leave your room, turn right and enter the third door left. There is a radio on the table. Simply turn it on and listen to it.
door to enter
radio on the table

After you escape a bear attack, you spend a night in a stable. When you are going for the water, leave the stable, go left following the road. Go in the second house on the left side. There is a lighter lying upon the shelf. Pick it up, continue on the road and watch the right side. After passing a shed turn right directly to the church. There is a fallen wall on the right side, enter there and light up candels ahead.
house to enter
lighter on the shelf
path to church

Morning after sleeping in the stable you continue your journey. Further in the village you find a house with a fireplace still smoldering. Go inside, take an axe next to the door and look on the table right. You find a letter, which you have to pick up. Afterwards, push the closet from the door and open it. There is a grandmother sitting in the chair. Take the axe and end her suffering.
house with smoldering fireplace
pick up the letter first
then kill grandmother

When traveling on the railway, don’t switch the first sliding rail and go on. Eventually, you’ll find hanged bodies.
rail arrow you mustn't switch

After you get to the city just follow the path. After the playground go right. You’ll see an old man arguing with two young men. Go help him and make sure you do it fast enough, before your partner does, otherwise you don’t get the achievement and help anyway.
playground

Old man offers you to spend a night in his house. When you’re finished eating dinner, stand up, turn back and go to the child. He asks you to help him. Succesfully assemble the puzzle.

When you have a flashback about your wife, instead of calling her, call 666-66-66.

After you escape from the van, run through the container at right. There is a first aid kit that you need to pick up, if you haven’t got any. When you escape completely, your partner lies down behind the container and asks you for the first aid kit. Give him one.
you can pick up first aid kit in this container
help your friend here

After the cutscene when you come near the pension Bor, instead of going inside, turn left. Pass bus wrecks and follow the corridor at the very end. Watch through the cranny and enjoy the easter egg.
Go left right away
Continue untill you reach the end

For this, you’ll need to find a car battery. First, you should try to search in the cab in front of the pension. If there is nothing, you need to scavange pension interior and the neighborhood (or you can reload the game and check cab again). In pension be careful and watch for traps. If you see them, jump over. As soon as you get the battery, go to the second floor, cut the tape on the door and go to the big hall. Continue downstairs and to the left. Keep watching for traps. At the end of the hallway, there is a room with projector. Attach the car battery to it and see, what the code is. Remember four numbers in circles. Then go back to the top floor and find the room with safe. Use a code and open it.
cab with usual battery spawn
if it's nothing there, you'll have great time searching
watch out for traps
enter this door at the first floor
by cutting the tape, continue downstairs and left
attach the battery
remember four numbers in circles
find a safe at the top floor and open it

There is a strange picture hanging in one of rooms at the first floor of pension Bor. Stare on it for a while.

Before you enter the subway, you‘ve been told to stick left if you come to any crossroad. When you come to red light, do the opposite and go to the right tunnel. You’ll hear anomalous sounds which scare you.

After you escape from flying lights, continue untill you see a cloacked figurine. Open right door and go in. You’ll see something like military transmitter. Turn it on.
choose the door at right

After a cutscene where you jump down and search the corpse for AK-47, you’ll have to fight five dogs. There is a full magazine in the rifle already, so you don’t have to waste time picking them up. Instead, quickly run to the corner you came from and then shoot each wolf in the head with 4-5 bullets. That way you don’t need to reload.
cutscene when finding armed corpse

After you leave subway, turn right and look for a house with an open window. Enter it and go to the kitchen. There is another open window, leave through it. Continue downstairs.
open window
find kitchen and leave there
downstairs you'll find mannequins

Go back to the house you went through to achieve „I hate mannequins!“. Look for the passport lying somewhere. Pick it up and remember four numbers in a circle. Pass the city in the direction to your flat. The safe is located in the house opposite to your house in the second floor. Go upstairs and then open door at right. Find a safe in last room. Use the code and open it.
passport with four numbers in circle
house with safe

As you play, do all side things that don’t really affect the main story, but show in your way. Pick up letters, listen to every radio, help other people. This behavior ensures you the good karma. Don't stray though, stay on the path.

Play the game and only care about the main story. Though, you can still kill grandmother, give your friend first aid kit and open safes. But don’t pick up anything at all and don’t listen to any radio.

This requires you to play the game exactly as told below.
After the first cutscene, take a first turn right. You’ll come to a house with car. Go inside and pick up letter from the desk.
house with a car
letter on the desk

While dreaming about hospital, there are some notes to pick up too. Enter second door on left and look into the drower left. Then continue to enter third door left and turn on the radio (What happened?). At last, go into third door right. There is a patient card on the table right and a letter lying in front of the corpse.
second door left, in the drower
third door right, on the table
third door right, next to the corpse

When spending a night in the stable, go light candels (The faith in God will help us). In the morning, go on and after you pass an arch, take a look into the first house right. Care for a trap and then find a piano. Play on it four times. Then follow the path to kill grandmother (Raskolnikov). Go back on the road and turn to another house left. Enter the room at right and pick up newspaper.
pass the arch and turn right
care for traps
play full song on the piano
continue to find this house on the left side
pick up newspaper inside

After you reach end of the railway and enter the city, make sure to be first one helping in the brawl (Hero). Evening, after you’re done eating diner, help child to assemble the puzzle (Remember childhood). After you do it, look to the left. There is a letter lying on a shelf. Then move outside and go to backyard, behind the outhouse. There is a ballerina gadget. Open it and watch. Then you go to sleep, but before you enter room with bed, straighten the crooked image on an opposite wall.
letter on the shelf
behind the outhouse
there is a ballerina to watch
crooked image

When escaping bandits, follow instructions to help your partner (Friend).

As soon as you get to pension Bor, head left to the end of corridor (Small world). Then keep looking for a car battery to be able to open the safe (Top secret). Look out for traps. After you opened the safe and have taken everything (or letter atleast), at the same floor look for the letter lying next to the corpse.
letter on the floor

After going into tunnel, look right to see door with a number 17A. Enter it and at the table right, there is a newspaper. Read it. Then follow the way and listen to the military radio (What the numbers mean?). After you get across the water, before you open the gate there is a barrel with a letter on it. Pick it up.
door 17A
newspaper
barrel with a letter

At this stage, it’s already been decided which end you’ve achieved. Depending on the cutscene you get after the nightmare in subway.
cutscene with your partner

I only chose to show stuff that have direct effect on getting karma! Yes, I am aware there have been other letters, radios, instrumentals and photos. But they shouldn’t be affecting the ending at all.