With the release of the DMsguild I published an adventure called Elfhunt. Now other of our gamemasters are also interested in publishing a variety of things, including adventures. In that respect I've been asked how I set up my adventures. As an engineer working in R&D I have a very structured workflow when creating an adventure that I thought I would share with you today in a series of steps.
Step 1: Idea
D&D is an open game. Anyone can be a gamemaster and anyone can create their own adventure. When you create an adventure to be shared, you publish an idea. When you have an idea you can write a hundred pages about it or simply take a walk. Personally, I write a few notes on a piece of paper or my whiteboard.
Step 2: Flowchart
The Dungeon Master's Guide is a great tool to help you create an adventure. On page 72 they mention adventure types. In my opinion, the first thing you need to think about is whether your adventure is a location-based or an event-based adventure. Both of these, however, follow a certain flow. A location-based adventure requires you to create a flow through the locations while an event-based requires you to create a flow through time. In Elfhunt, for example, I created a flowchart through a variety of events.
If you have an idea of how long your adventure should be, then assume 1-2 hours per location or event, and you should set aside 1-2 hours for the beginning and the end. Note that this may vary form DM to DM, but also remember that it is your job as the gamemaster to get the flow of the game running and not simply let the story stagnate in one place for too long. When you write an adventure, take these facts into consideration.
Step 3: Encounters
Now for the bulk of the adventure. For every location or event I usually start by writing a sentence or two that describes when, where and why this happens. Then I have a box with a read-out text for the DM. I sometimes use it myself, but in my experience this is a great tool to add in published adventures. Then I describe in detail the location or the event and why it's part of the adventure. If there's a combat, I add the monsters. If there's a trap or a skill challenge, I write down rules about it or refer to what rules to use. If there's a puzzle or a riddle, I note it down. I usually end the encounter with a note about rewards and what happens afterwards. This may include XP, treasure, and what possibilities the players have afterwards.
Step 4: Fill
Once you've filled up your encounters, you'll notice that there are points in your flowchart that haven't been filled. This usually includes towns and NPCs, which are used to give hooks (which also needs to be added ), NPCs that serve as merchants or a source of information, or a place to rest. It may include cut scenes and other such things. Write a paragraph or two about each of these. If you are inspired to write more, do so, if not, then a single paragraph is usually enough. Remember to describe visually and in detail what you are explaining to your readers.
Step 5: Intro and Conclusion
To finish off an adventure you need the introduction and the conclusion. This usually includes the introduction that explains what this published piece of writing is, a background explanation to why this adventure is happening, an overview of the adventure, and possible a prologue and/or a description of how the adventure should be used or run. The conclusion includes everything from a total reward (XP, treasure, renown, etc), what happens next, maybe an epilogue, and definitely appendix. In the appendix you should add new monster stats, magical items, maps, and other relevant pieces of information that you haven't found a place for in the adventure.
An alternate route
As an R&D engineer I need to be flexible and sometimes a project takes a completely different route than the structure I've presented above. My greatest advice to anyone who want to write and publish adventures is to follow your inspiration. If you have no idea, but feel like drawing a map, then do that first. Put that map into the appendix or write some text about the map and put it into the "fill" in the introduction. The map may lead you to get inspired to run an adventure on an island in the middle of lake, which may lead you to write about a nearby town and a ruined castle on the island which includes all the encounters. In the town you may then want to add NPCs to give the players a hook or two to go to this island in the form of quests. You may then feel like you want to add a few encounters on the trip to and from the island, and before you know it you have an entire adventure.
Take it in steps. Don't try to write everything at once. Follow your inspiration and try many things. Eventually, you'll write something awesome, and even if it's not awesome, publish it. Others may find it better than you do.