WARNING!: THIS GUIDE CONTAINS SPOILERS. AS YOU NEED TO DO MORE THAN ONE PLAYTHROUGH TO 100% THE GAME, I ADVICE YOU TO CHECK THIS GUIDE DURING YOUR SECOND RUN.

A general tip for many of these achievements is to press Esc/Y to save and quit if you don't get the desired result. The game will start you off right at the beginning of the scene so you can try again.

For some of the achievements you don't need to do exactly as the guide states (e.g., for the hangout achievements you just need to do 2/3 events to get the final event, including the achievement), but seeing as you need all journal entries for Seriously?, I have left in information that will ensure you don't miss out on too many entries.

If you're interested in talking about the journal entries, achievements, etc., then feel free to join this Discord server: https://discord.gg/rcrm4gS

Welcome Back!
Story-related progress.


What???
Story-related progress.


The End
Story-related progress.


Changing Of The Seasons
Story-related progress.


Echoes
Finish the four dream sequences.


At The End Of Everything
Unlocks after the credits.

Bass Ackwards
Mess up on all of the songs during band practice in one playthrough by not touching your keyboard/controller or smashing random buttons. Playing Mae's bass in her room screws it up, so avoid it.

Maestro
You "only" need to play all three songs during band practice at an okay level. While the first two ones are doable with practice, the third one may be troublesome. If you, like me, used a controller to play the game, consider switching to keyboard and remap the bass strings to HJKL! Playing Mae's bass in her room screws it up, so avoid it.

~*~Demonpower~*~
Just beat Demontower, which is a minigame on Mae's laptop. Doesn't matter which ending you get. However, I suggest you go for the good ending which will give you 2 achievements at once (see Palecat).

Palecat
Beat Demontower and get the good ending. DON'T kill the bird that spawns during lv. 2; he will give a hint every 2nd level for which skulls you need to activate on lv. 10; beware the order! After you activate the skulls in the correct order, a tomb with a key will spawn. Pick up the key, go up to the big corpse and use the key to close the wound. Then proceed to beat the final boss and voila!

Hold Onto Anything
Beat the game a second time. For some people it currently only works if you hang out with ONLY Bea or Gregg.

RABIES!
Hang out with Germ under the bridge and come back and sit on the bridge the next day. After a while, Rabies the Trash King will show up and the achievement unlocks after you talk to him.

Dusk Stargazer
Look at stars with Mr. Chazokov. He will hang out on top of the poet's house on some days; just check every morning and on the last day! After you hang out with him 5 times (9 constellations in total), the achievement should unlock.

The Tooth
Keep checking grandpa's bookcase (next to the bird cage in Mae's house) and at some point you get some numbers. You will also have to bug your dad to move the boxes in the room underneath the stairs; keep watching TV with him (3 times). After he moves things out from the room (the game will let you know when), go in there, crawl to basement, open the lock, and grab the tooth. You also need to go to the library with Bea to learn about the tooth by reading a newspaper clipping on miners and strange teeth. On the last day when you talk with dad outside the front door, Mae will give him the tooth and the achievement will unlock.

Poets Of Possum Springs
Talk to Selmers (the bear in the pink hoodie) and listen to her poems everyday. When you're done with the research at the library, the Poets of Possum Springs will read their poems next to the reception desk. Listen to the poems for the achievement.

Best Available Friend
Hang out with Bea instead of Gregg. Follow her storyline (mall, house call, dinner, college party); it will unlock after the college party.

Crusty
During the pizza eating scene, only eat the leftover crust.


Mother Of Vermin
Feed the rats one pretzel from the pretzel stand. Climb the powerlines to the left of the stairs to the church, follow them until you get to the building with the "Nuke Possum Springs" graffiti. Get on that building, then go all the way to the right until you reach a half-open window. Climb inside and you should find the rats inside a deceased mascot!

Miracle Rats
Same as above, just feed them over the course of three days and they leave the nest to cause a major rat problem.

Horrorshow
Talk to Lori on the rooftops every day/near the war memorial and go to the train with her every time. The achievement pops after your last talk. To find her, follow the route outlined in Mother of Vermin, but continue right and keep climbing until you see a mouse chilling on the roof.

Let's Be Legends
Hang out with Gregg instead of Bea. Follow his storyline (Food Donkey, parking lot, woods, donut shop); it will unlock after the donut part.

Brainshot
Shoot the target in the head when in the woods with Gregg during his storyline.


You killed that poor roach.
When you find the arm on the ground, there's a roach running around that you can poke and squash with the stick.

Deep Hollow Hollerers
Get the two lonely musicians together. One is in the secret stage (top of tall building near the Snack Falcon), the other will appear on the rooftops not long after Harfest. Talk to the violinist first both days, then go see them on the stage on the third day.

Thryy Wyrd Tyyns
Talk to some weird teens hanging out by the cliff past the church during Halloween (choose shipwreck). They give you a side quest to find 3 pentagrams. The first is if you go to the out of town party with Bea and talk to the punk girl in the back of the room OR order Doomnuts with Gregg during his storyline. The second is in the secret stage (see above section). Third is at the very end in the mines. The achievement unlocks the next morning.

Knife Fight
Win the knife fight against Gregg in the forest. You just need to win most rounds.


Accidentally Good Dinner
Go shopping with Bea after work one night and pick out chicken, biscuits, mac n' cheese, and cream of chicken soup for dinner. This is just one of many possible dinner combinations.

Jenny's Field
Talk to your mother everyday at church after you get access. When she asks you if you want to get out of there, say yes and finish the event.

He's from somewhere.
Hang out with Germ whenever you can before you go hang out with Bea/Gregg (3 times in total). When everyone groups up at Gregg and Angus's apartment, he will strike up a conversation before leaving, and it will unlock.

Make It Last
Do all the following (Confirmed by the devs!):
- Bea and Gregg Friendship Quests
- Angus, Bea and Gregg Investigation Quests
- 3 Germ Friendship Quests
- Found all Dusk Stars with Mr. Chazokov
- Fed Mallard Rats to the point where they appear in town
- Found Three Pentagrams
- Reunited the musicians
- Gave Dad the tooth
- Selmers Poetry Level 3

Seriously?
Fill out your journal completely by getting all doodles over multiple playthroughs.

Here's a sheet showing how to get all doodles and with links to images (credit for this goes to Lyze, Foxy, Cherry, Cr4zy4zn, and myself!):

https://docs.google.com/spreadsheets/d/1Sd_ME3FTPdHLjkV0URGOwI8SUyOjXMT9Mi56AvGILSA/edit#gid=0

Note that the Weird Autumn update added around 7 doodles that have been reported to not count for the achievement.

Note that you need ALL three robot heads from Gregg's first event. An easy way to quickly get all heads is to backup your save file at the beginning of Gregg's first event and copy it back into the save folder after getting the first head to get another.
The saves for NITW are stored in the default Unity save location: C:\Users\User Name\AppData\LocalLow\Infinite Fall\Night in the Woods.
Your save is named "player.dat", while "persist.dat" keeps track of your progress (DON'T touch persist.dat!). You can copy your save file (player.dat) to your desktop, go play the event and get a head, copy the save file on the desktop back into the folder, play the event again and get the next head, etc., and there you go!

The achievement unlocks after the game automatically saves. E.g., if your final doodle is the musician one, you will get it when you leave the secret stage.

Thanks to all the people on the forums/this guide who've shared their wisdom! This includes Zaltys, Venceremos, chinewbie, The Phone Boy, Link, Bob, Furlop, AidsBolaPoxFlu, zFcBoxhead, RedCervidae, Alice, Lumi, damnitreid, Ayon, Lumberjack_Lim, Goat Boat, Jovian, NoelDeirrow, None Pizza with Left Beef, Era Extraña, StealArty, ツPImPツ™, BlackRose, Benji that ffffing furry, ToasT, Desty, and Mae!

Also special thanks to the NITW Discord group (Cherrybomb, Lyze, Foxy Granpda, and the rest of you lovely nitwits), D. for the thumbnail/banners and Alec, Bethany, and Scott for making this wonderful game! <3

Rest in peace, Alec Holowka.