One-page dungeons are a challenge for GMs. You need to think on your feet. There's just enough information to get you started but you'll need to improvise, create stats, and answer questions without hope of finding answers in the text.
Here are my standards for deciding if something goes into the folder.
Does the art and/or map complement the text?
There's so little space in a one-page dungeon that sacrificing a huge chunk of it for a series of blank rooms seems excessive. Art is hard. My one-page dungeons don't usually have any unless someone talented steps up.
The map or art should enhance the text without repeating it. If possible, it should add more colourful detail and things to riff off. The highest possible ideal is to have a one-page dungeon where either the art or the text could be run as a standalone item.
How is the information presented?
With limited space, bold sections, headings, and careful use of paragraph breaks become vital. Bolding monsters and italicizing treasure is a start. If there are rooms, is information presented from most relevant to least relevant (general impression, movement, enemies, smells, sounds, details), or at least in some sort of logical order? The smaller the font size, the more vital it is to present information clearly and concisely.
Are the tone and theme consistent?
If I skim the dungeon and mentally file it away as a pseudo-medieval semi-realistic adventure, will I get a nasty surprise when the Lunatic Lemur Legion attacks in the last room? Can this dungeon be integrated into a campaign without too much effort? Are dungeon-specific words and concepts described in enough detail?
Is there tension?
It's easy to accidentally write a one-page dungeon where there's nothing to do. Some NPCs, some enemies, some treasure, but no tension, no held kinetic energy. A one-page dungeon should feel unstable and interesting. One of the weaker Trilemma adventures I've run was The God Unmoving. It's a great location. There's lots of cool detail but it's fundamentally a stable environment. There's no obvious reason for the PCs to interfere or set things in motion, or chances to play one faction against another, or come up with a really cunning plan to exploit the situation. It was still a great session but wasn't quite what I'm looking for as emergency adventure fodder.
Is the dungeon better than something I could improvise?
This one's a given. If the dungeon is called "Flying Cottage of the Bakery Witch" and I could improvise a better dungeon based on the name alone, it's not going in the folder.
The Trilemma KickstarterMichael Prescott has a Kickstarter up. You might want to consider backing it. Beautiful art, linked adventures, an index, an implied setting; it's got it all. It's also much nicer to use than a folder full of loose paper.
Full disclosure: I wrote one of the one-page dungeons in the compilation. The original plan was to see if Michael was interested in commissions and then paying him to do the map. Things went a bit differently.
Trivia: Room 2's description is "Grand Foyer: Arches, vases, dead ferns, old paintings in gilt frames." I'd intended "arches" to imply height and solidity, like arched ceilings and doorways. Michael interpreted it as "big mysterious stone arches in the room" in the art. And that's way better. In tests, the mysterious arches of standing stones have come up every time. Cultural memories of Tomb of Horrors, I suppose.