As the description mentions, I have used a LOT of spoiler tags, so you can avoid seeing more than you want to see, while still knowing when you are coming to a watershed moment that will mean you will have missed your chance at one or more achievements. If you want one that is easier to read, I have posted the same guide with the moments and achievement names un-spoilered under the name "Spoiler-Lite Missable Achievements Guide". :-) Which one you prefer is entirely up to you. The moments to watch for are in chronological order, so as long as you only read to the next ►, you should avoid spoilers to the extent possible without missing anything.

► Lines like this are the moments you need to watch for, because certain achievements will be missed if you haven't gotten them by now, or you have to do them at exactly this point. I have made these as un-spoilery as possible without just being confusing.

> Lines like this are the achievement names themselves. Not terribly spoilery, but give a bit of a hint about what you need to do.
Right below that will be lines without a mark, which are the specifics of what you need to do to get the achievement. Pretty direct, therefore spoilery, but you might need to look around a bit to find the relevant items.

There are a few of moments that are the cutoff points for multiple achievements. I just list them all out in rough chronological order- you can do them in whatever order you like, and I recommend poking around to see how many you can trigger on your own without using the guide first, as there are a lot of fun little messages and interactions in this game, especially if you recognize the references in the house, but not only then.

► Before flipping the breaker:

> MAY I HAVE THIS DANCE?
Tap-dance and ballet at the dancers in the basement.

> THEY'RE STUFFED (part 1 of 2)
One part of six: Use dog treats on the narwhal to the left of the hula dancers in the basement. The other five taxidermied animals you need to "feed" for this achievement can (or have to) be done later, and are mentioned below, but don't miss this one!

► Before Filling a pouch with correct marbles.
>RED AND GREEN HERRING
Fill a pouch with two cat's-eye marbles.

► Before sending out the first pigeon- Jude needs to do something four times over the course of the next bit of game, and it's easy to miss the last repeat.
>THE LONG GONEBIRDS
Examine Jude's bird cage before sending out any of the Lone Gunbirds, and after sending each one out, including a final time during the living room Strife Sequence.

► Before taking the attic key:

>HOPE SPRINGS ETERNAL
Use the ballet shoes on the slinky up near the attic.

>DON'T ENCOURAGE HIM
Give the Bubsy poster by Joey's TV some dog treats.

>NO. THEY'RE YOURS NOW
This is tied to an action that affects two mutually-exclusive achievements that don't pop until the end of the game. I suggest getting both and labeling the saves, because it is implied you can carry over your save to the next game, and that these will have different effects.
To get this achievement now and CELL YOU LATER at the end of the game, take the E Cell batteries from the Universal Remote on the table by the television in the living room, then try to put them back.
To get BATTER LUCK NEXT TIME at the end of the game, just leave the batteries alone.

>WHERE THEY BELONG
Throw some pogs in the trash, by the fridge in the kitchen.

>PERIOD-APPROPRIATE REFERENCES
After getting the power back on, fax some pogs using the fax machine by the fridge.

>THEY'RE STUFFED (Part 2 of 2)
Attempt to feed dog treats to the taxidermied bear and bear-deer hybrid by the front door, the winged bear clock near the door to the Trophy Room, and the lioness head and deer in the Trophy room. If you also fed the Narwhal in the basement, the achievement will pop when you have finished feeding these.

>BIRDGEONING TALENT
Use Byers on the piano and listen to his actually promising performance. He's also amusing to use on pretty much every random thing you come across.

► Before firing the third flare:

>ACTIVITY RECORDED
Locate the mysterious figures out the hard-to-see window in Jude's treehouse. It's the red patch just to the left of the binoculars. There are other things to look at all around it, so it might take a few tries to click on.

>SEQUENCE BREAKER
Try firing a flare at the evil-looking mansion out the hard-to-see window in Jude's treehouse. It's the red patch just to the left of the binoculars. There are other things to look at all around it, so it might take a few tries to click on.

► Before activating the thing under the fluttery sheet.
>SERIOUSLY, DON'T EAT THE MUMMY.
Use spice mix on the mummy hidden in the attic. You can really only see its legs, sticking out under the chair between the pile of hay and the second-best shotgun.

► While using the tablet after looking at the map. Only one chance, so maybe save if you're going to try this one on your own.
>MELODIOUS CHIRPS AND TONGUE-CLICKS
Tell Xefros you're the nightmare squid god kind of alien.

► Before picking up the white box that voops in.

>CONVEXED
Use the bent spoon on the pile of bent spoons.

>PLAYING WITH POWER
Use the cuebat with the pusher playbook.

► Before treating the deercat:
>VENT FRUSTRATION
After crawling through the vent, send Byers back the way you came.

>JUNIOR VETERINARIAN
Use the bowl of milk, dog treats, Alternian bestiary, and Alternian veterinary kit on Byers. The milk must be in the bowl to proc this achievement.

>SURELY HE HAS SOME ADDITIONAL PURPOSE
If you haven't used Byers on at least 30 objects by now, do so before feeding the Deercat. And you've missed out on a lot of usually-amusing messages.

There's one achievement that you just can't get yet, and I suspect won't be available until the last game in the series comes out- BOROS. Thus, don't sweat that one yet.