In keeping with the theme of the game, I will be trying to keep these as non-spoilery as possible! Part of the fun is working it out for yourself. Sometimes that means the hint will be to get you to a spot where you need to take one more step on your own.

In general, the best way to progress is to keep looking. If you get stuck, you can ask the rubber duck. Don't worry, there's no "hintless" achievement; any help you ask for is strictly between you and the duck.

EDIT: Thanks to Ticcory for help with the Search Failure achievement!

These are unmissable.

You Deserve a Gold Star
Find everyone on the first piece of paper you're given.

Establishing Roots
Find everyone in the oldest group photograph.

Branching Out
Find everyone in the middle group photograph.

Take My Hand Beneath the Tree
Find everyone in the latest group photograph.

Family Secrets
Finish the main game.

Audiophile (preparation)
There are three playable songs in this section, which you'll need to unlock this achievement later.

"I can't figure out how to play it!" hint: If you don't immediately see a play button, it's not playable.

Call Screener
"Screening" a call means letting it go to the answering machine.

Duckler County Denizen
What exists in our world, but the characters in the game The Roottrees Are Dead never reference, and not just because it's the 90s?

Extra hint: It's not any of the characters or places in the game, because you find out about all of those from the characters of The Roottrees Are Dead themselves. So what's something related to The Roottrees Are Dead that exists in our world, but the characters aren't aware of?

Extra extra hint: I suppose I'm being a bit cheeky; there's an unnamed character in The Roottrees Are Dead who says it out loud but doesn't know what it means, and "you" mention it in passing when you look up a certain periodical...

Extra x3 hint: You've definitely read the search term. A lot. You've likely either clicked on it or typed it in, too. It's probably on your screen right now, so you may have even read it in the past 30 seconds.

Genealogy Genie
Getting this is difficult, but I promise working it out for yourself is rewarding. If you get Loose Ends, you'll have all the tools you need. What held me up the first time I played was, I didn't apply the tools I knew I had. Read carefully, interrogate your assumptions, and maybe make some notes.

It's All Connected!
This achievement must be gained in the base game.

That comment you read on the radio station's website seems interesting. You should really look into it. Surely you'll find something useful if you just search for all of the Conspiracy Theories...

Extra hint: That wasn't a typo. They're all capitalized.

"But I'm sure I did them all!" hint: Even though it'll show the same result, "4-day" isn't part of the conspiracy's name. Silly, I know, but I didn't code it.

"But I'm sure I did them all!" hint 2: Brand names can have conspiracies, too.

Loose Ends: Part One
Find all the evidence in the main game. There are 38 items.

Search Failure
There are two ways to search for something: in the browser itself, or by highlighting something in your journal.

Extra hint: This achievement wants you to try to search while offline. But if you try to open SpiderSearch, the internet turns back on. How might you combine these pieces of information?

Thinking Outside the Box
Hunt for achievements.

Extra hint: What do you usually do in the game if you want to find something?

Second verse, same as the first: unmissable.

Old Flings
Find everyone on the left.

Extracurricular Activities
Find everyone in the middle.

Roottree Company Affairs
Find everyone on the right.

The Big Reveal
Finish Roottreemania.

Audiophile
Including the three from before, there are five playable songs. Every musician we see in the game has at least one musical track you can listen to. You sure there isn't someone you're forgetting?

Extra hint: Maybe someone whose track you wanted to listen to back in the main game, but you couldn't find online?

An extremely vague list of the five songs so you can check what you might be missing:

• A song about skating
  
• A song about trees
  
• A song about someone's mom
  
• A song that mentions a spoon
  
• A song whose lyrics include its title a lot

FamilyDoku!
Have you looked around your room lately?

Loose Ends: Part Two
Find all the evidence in Rootreemania. There are 43 items.

Voracious Reader
Keep looking, ask the duck.

What's the Deal With All These Roottrees?
This achievement can't be unlocked on a completed save. Also, the solution can only be accessed in Roottreemania.

You can complete this one on a fresh Roottreemania save file in like five seconds. You don't even need to type.

This achievement involves a reference, and how to use it.

Use hint: I'm serious, open a fresh save and don't touch the computer. What actions are available to you from the start of Roottreemania, but NOT the base game, that you can combine with the reference?

Reference hint: The answer involves a real person's name. Someone who says "what's the deal with" a lot.

For Americans under 25, or people not familiar with US media, this reference may be legitimately tricky, so here is an extra push if you don't want me to just tell you: You could try looking up that phrase in a real search engine. He also did Bee Movie and has a sitcom on NBC that shares his name. Wikipedia has articles on them.

But if you do want me to just tell you the reference: The real person's name is Jerry Seinfeld.

"But I'm sure I did it!" hint: It has to be a key relative.

Hinting at cultural references is really tricky. I'm not revising this further. If you just want someone to tell you how to solve this, there's another guide that explains the exact steps.

Where There's Smoke...
Keep looking, ask the duck.