All the unmissable achievements:

"Knock, Knock":
Entered the Fretland Farmhouse
Earned during day 1, when you first enter the Fretland Farmhouse

Blue Skies in Norway:
Good morning, Edward!
Earned during day 2, when waking up

Home alone:
They're not coming back, are they?
Earned during day 3, when waking up

Everything Changes:
...and we're definitely not alone.
Earned during day 4, when waking up

"I am not alone"
Everything changes, again.
Earned during day 5, when waking up

Awakening:
Edward is born anew.
Earned during day 6, when waking up

Goodbye to all the things:
The end.
Earned during day 6, when leaving Graavik (Grey-woke)

All the missable achievements and how to earn them:

Piano man:
Played the piano.
Can be earned from day 2-6. Go upstairs in the Fretland Farmhouse and play the piano in the first room

The Artist:
Completed all the sketches.
Can be earned from day 2-6 (after obtaining your journal in day 2, before fetching your suitcase in day 6) Interact with all "Draw"-spots:

1. In The Fretlanders House, upstairs in the Piano-room (First room by the top of the stairs) there is a chair pulled out from the table. Interact with it and start drawing


2. Upon exiting the Fretlanders house, go straight to the right (still within the borders of the Fretlanders fence), and interact with the well. Draw here


3. Leaving the premises of The Fretlanders yard, go to the right, following the stoney fence. Approximately halfway down the fence (overlooking the village) you can sit down and draw. Draw here.


4. Continue down this path to the church. When entering the graveyard go straight to the right. You can sit on the stone fence behind a knocked over wheelbarrow. Draw here.


5. Go back away from the graveyard/church the way you just came from and move through the village. On your left side after the village you will find a small stone circle (Sonehenge-like). There will be a small stone next to these which you can interact with. Draw here.


6. Going downhill from the stonehenge, stick to the left path and you will see a waterfall. A rock nearby can be sat upon. Draw here.


7. After drawing at the waterfall, turn 180° and continue, following the right path. You will find a wooden bench, before reaching the "Frederik Fretland og Søn Landhandleri". Draw here.


8. Continue past the "Landhandleri" down to the pier and interact with the small wooden crate on the pier. Draw here


9. Turn left towards the mine and go near the abandoned minecart. When you look to the right, you will see a small stoney island just off shore. There is a small rock overlooking this, near the water. Draw here.



Co-dependent
Lissie's getting a bit tired of you, Teddy bear.
Can be earned from day 1-6. Talk. Keep talking. And talk some more. Will be achieved by repeated talking with or to Lissie (or calling for her repeatedly)

The Conversationalist
Exhausted all Lissie conversations.
Must be earned from day 1 through 6. Everytime you can talk with Lissie, make sure to say everything possible by pressing the Speech/Call button (F on keyboard, Right shoulder on controller) until Edward starts repeating the prompts he has already said

To Ruth, from Edward
Good night, little girl.
Can be earned in day 6. Head upstairs to Ruth's room and interact with her bed.

Life is but a dream
Row, row, row your boat.
Can be earned after day 6. When getting in the boat to leave Graavik (Grey-woke) don't press any buttons. Let the credits roll. When the screen turns black, let it be for about 30-45 minutes, until the game returns to title screen by itself.
NOTE
If you are using a controller with an automatic standby/turn off setting, it might be a good idea to turn this off.
Some players have reported that if the controller turns off, the game registers this as an input and you will not receive the achievement.