This is the second part of “How I write an adventure”. Part one might have been a little bit simplified, but it wasn't (just) a cheap joke.
Those really are the two steps: Make a skeletal frame and write the rest of the fucking adventure.
Step 1: Making a skeletal frame
Based on the diagram previously this may seem like the simpler of the two steps. It isn't. This requires inspiration and vision. You sit down at a blank piece of paper and decided what is the point of your adventure. Why are you writing this down in an almost endless sea of adventures both published and not. What are you trying to do with it? Write down that purpose. Then add additional reasons until you start to get a useful framework to add content with (I like about 5 rules, usually between 3 and 7).
Here are two examples:
It has to be a re-playable by the same group.
It has to be quick to prep, no massive piles of tables.
It has to involve uncertainty
It can't be about the end of the world
It can't be about death as the risk
It has to replace a “GM info dump”
It has to reward players to “play along”
It has to lure players to want to keep exploring the site
It can't be a railroad
It has to have things to tinker with
For each adventure I would use those skeletal rules, branching from spine to finger bone in importance, and use them to hang content from (or as a reason to prune unwanted content). Notice that each of the rules are about its use is in the context of a game. I don't have things as part of the frame like “Giant spider” or “Crazy wizard” or “Journey to the center of the earth”. Those are the content. The framework is the reason for the content.
Dunnsmouth has (spoilers) spiders, and secret cultists, and infections not as the purpose for the adventure, but as content to hang on a skeletal framework of other ideas. The primary reason the adventure exists isn't to showcase the cool content but to be enjoyable to play as a game. The content supports the point of the adventure, not the other way around. Its all about interest and fun at the table.
Step 2: Write the rest of the fucking adventure
Now that you have a reason for the adventure, dig through your notebooks and past and future campaign material for big chunks that will help you support those ideas. Rip out big chunks of meat and slap them on the framework, always making sure it doesn't violate any rules unless it somehow greatly improves a more important bone. For Thulian Echoes there is a little bit of railroad in regards to the past adventurers in that they always die, but that is acceptable because it greatly supports bone 2 in that it is used to get players to “play along”. Also if I go through my “portfolio” of past gaming material I can ensure that I only rip out the hunks that work at the table to staple into my frankenventure.
Then I smooth all those hunks of flesh into an “I can't believe its not human!” pile.
At that point, it is time to run through a playest and see what gaps you need to fill with more content. Start stitching up that pile of adventure cadavers until things stop sliding off. Cut anything that turned out to be rotten and replace it with new content appropriate to the rest of the form.
Run another playtest to be sure, repeating the process.
Now its beginning to seem more slick.
You know what, maybe too slick. Add some fucked up shit and run through another playtest.
There we go. Now comes the final part required only if you want to get published or self publish this.
Actually write the rest of the fucking adventure. This isn't in itself hard, its just boring as sin. You go through each room, each description, each item and you put to words all of those things you have currently as jot notes like “big dude, leather and bow, skull mace with the cool mind power”. You write a paragraph or two that is actually useful at the table instead. You flesh out the wandering monster table and actually describe in better detail the treasures and monsters. You skirt along the edges of what is minimalism and what is just useless. You do all that boring stuff you don't want to do and the only way to get it done is to actually just sit down and fucking do it.
Draw that fucking owl, no one else will draw it for you.
Now wait a week and go back through and cut out the garbage that doesn't need to be there. Cut it like its a cop and you've been going by Mr. Blonde as of late. Half of it is trash you forced yourself to write so you would have something there to check off the mental checkbox of finishing that part of a task so you can move on. Wait another week and do it again.
Now you have written an adventure. Now look into pitching it to a publisher and maybe getting an editor.