What follows is my summary of Bryce Lynch's 30 (as I count them) principles of adventure design, based on these and other posts from his excellent blog, Ten Foot Pole. I have divided the 30 principles into 6 categories, starting with General Tips.
1. General Tips: The 5 C’s
1. Color: The referee should give brief but evocative descriptions of locations, monsters, NPCs, and treasures. Avoid the vague or generic.
2. Context: In order for their actions to be significant and purposeful, players must generally have some information about the likely consequences of their actions, such as likely reactions of monsters or NPCs.
3. Choices: There should be more than one course of action available to players in order for the adventure to continue. Avoid choke points—both literal choke points in the physical layouts of dungeons and other locations, and figurative choke points which require a unique decision or solution in order for the adventure to proceed.
4. Consequences: Player actions should be allowed to make a real difference in the adventure and in the campaign. Avoid a set storyline or sequence of events immune to player interference.
5. Creativity: Related to (3) and (4), reward player creativity by allowing them to pursue unanticipated courses of action or to produce unanticipated consequences, rather than restricting player action and player creativity by setting up arbitrary constraints in the location layout or course of events.
6. Don’t rely on a single hook; use multiple kinds (treasure; reward; magic; glory; political power).
7. Create a rumor table with hooks and color.
8. Hooks should appeal to the players (not just their characters).
9. Hooks can and should be made complex / nuanced; e.g., working for an evil NPC, or working for rival factions.
10. To support sandbox play, particular dungeon, town, and wilderness locations, monsters, and NPCs should all have hooks.
3. Locations (Dungeons, Towns, Wilderness, etc.)
11. Location descriptions should be terse (not verbose) but evocative (not boring, obvious, generic).
12. Only include background info that affects gameplay. Avoid long descriptions of irrelevant info.
13. Rooms should have features that players can interact with to produce meaningful consequences. Give concrete descriptions of secret doors, traps, etc.
14. Floor plan tips:
a. Multiple routes (vs. choke points or linear, one-way paths).
b. Multiple entrances / exits.
c. Multiple stairs per floor.
d. Open spaces with balconies, galleries, and ledges at various elevations.
e. Pools and rivers that connect different rooms or levels.
f. Bridges and ladders.
4. Monsters and NPCs
15. Create interesting, believable motivations for monsters and NPCs.
16. Create factions of monsters and NPCs (which lead to a dynamic, interconnected strategic situation).
17. Give players the choice of allying, attacking, or having other relationships with monsters and NPCs.
18. Create schedules, routines, tactics, and orders of battle for monsters and NPCs.
19. Wandering monsters too should be given motives, goals, hooks, and tactics.
20. Avoid standard monsters. Failing that, describe standard monsters in a non-standard way (e.g., don’t just name their species).
21. Give evocative descriptions of monsters. Give concrete descriptions of their appearance and activities. Go for the telltale sensory detail, rather than the generic abstract trait. Show, don’t tell.
Example: Instead of stating that “One of the guards in the camp is a cruel bully,” say that “The burly Manfred takes a leak on poor Tobias’s bedroll, and then he snatches Tobias’s roasted chicken dinner from his hand and quickly gobbles it down.”
22. Use truly evil monsters to evoke a Sense of Terror.
23. Treasure should be valuable enough to motivate players and to make the challenges worthwhile.
24. Non-magical treasure should relate to the setting and give clues or information about monsters, NPCs, locations, etc.
25. Avoid standard magic items.
26. Give evocative descriptions of magic items. Give concrete descriptions of their appearance and how they must be manipulated to produce their magical effects.
27. Use magic items to evoke a Sense of Wonder.
6. Format and Functionality
28. Include the following kinds of reference tables:
a. Rumor / hook table.
b. Monster / NPC table which lists their main traits, motivations, location, etc.
c. Room / building table which lists the rooms in a dungeon (or other keyed locations).
29. In published modules, put maps and monster stats on separate sheets (so they are easy to refer to in play).
30. On maps, use keyed symbols to indicate standard features (e.g., lit/unlit, locked/unlocked, secret, trapped, etc.), rather than a verbal description in the location key.