This is going to be elementary for a lot of you, and a lot of modules say this stuff in the intro. But maybe someone out there missed the memo? You can’t just tear the shrinkwrap off a module and throw down some dice. Here’s my advice. Please do not consider me an authority on this; it’s just how I do it. I’m interested to learn how everyone else does.
1: Make sure everything’s there. This is more important with boxed sets and used material. You need all the maps, handouts, notes, etc.
2: Read through the module gently, as if reading a novel for enjoyment. Get a feel for what the module has in store and make some notes in pencil in the margins for things that don’t make sense or that are really damn cool. This is your book now, and it’s a workbook. You write in modules. You can try to keep your module pristine by using post-its or a separate notebook but it’s a huge pain. Also, it’s amazing to find a module in a used bookstore and find someone’s old campaign notes in it. You’re not only using the easiest note-taking method but enriching the future a little.
3: Read through again and pick out the actual challenges. Monsters, traps, obstacles, secret doors, puzzles. You can underline or put a symbol to the side in the margin. Make sure there are the right pegs and holes for your game system. Roll and write down HP for monsters if it wasn’t already done for you. For example, if you use 3E D&D, everything is going to need a DC. This is the stage where you convert the module to your system if it isn’t there already; usually theme and fat doesn’t change, only the bones, so you don’t need a deep appreciation of the module to accomplish it. Also, if this is as far as you get, you’re prepared for play better than if you mix up the order.
4: Now look over all the tools given to the players. These can include magic items, NPC help, hints, or just normal equipment. How will those tools help the party overcome the challenges? Does it seem like some challenges require the party to find certain tools first? It’s better if finding a tool makes the challenge easier, because clues can be like needles in a haystack for some parties.
5: Pick out the treasure. Note it in the sides.
Now you’ve read through the book once, and skimmed it three times. This is about as prepared as most module writers expect you to be. But you’re going to destroy their expectations in an exultant orgy of preparation.
6: We’re analyzing the module now. Back to challenges. Look over the monsters.
* Does each group have a motivation? Why are the Orcs here anyway?
* Are there interesting motivations you can give any individuals in the group? What is the Orc guarding the well trying to do around here?
* What will happen if these monsters are alerted to the party? If a fight happens in the guardroom, who can hear it? Are there alarms?
* What happens if the party fights a bunch of them and leaves? Do they re-fortify and what resources do they have for that?
* What happens if the party steals their treasure? Do they hang around, do something desperate, or emigrate?
* What happens if the party destroys them and loots? What, if anything, fills the void?
* What happens if the monsters achieve their motivations?
Next look over the other challenges with the same mindset. What if the secret door is left open? What if nobody can figure out the puzzle? What if the party burns down the palisade?
Now go over the tools. Are there obvious scams that can be pulled that will invalidate large sections of the module? Is that ok? Is it possible to use up a tool elsewhere and no longer have it for a challenge that requires it?
Don’t feel like you have to plan out everything, and definitely don’t try to create storylines that the players will follow, because it tends to reduce the game to a few IF->THEN branches. But thinking it through now might give you some really weird ideas that would be great in the game. For example, you might see a connection between the Kobolds and the Orcs where if they’re both kind of devastated they will join forces. Or maybe a band of thieves will call in mercenaries. But if your plan would be pretty obvious at the table, you don’t need to write anything down.
Now you’ve picked the module apart and figured out how it ticks. The next step is adding your own touch to the module.
7: Is the treasure appropriate for the challenges? Maybe you can hide extra treasure in places where players can find it if they play very well and creatively. What is the future impact of this treasure if the players use these characters in another adventure? It might be better to replace a permanent magic item with a charged one to limit its use to this adventure plus a few more times.
8: Are there any ways you can tie in your previous campaign events into the module? Can an informant, spy, assassin, or humble townsperson participate? Can you replace a flavorless flat NPC in the module with a cameo from a prior adventure? Try to figure out how the adventure outcomes will affect future adventures in the area. Mostly this will need to wait until after the adventure because you don’t know if the party will slay or join the bandits or miss them completely.
9: Read through again and find the places where there is very little detail. Maybe there’s a thief hiding in the storeroom. If there are a few traps that are identical, change some of them up a little – but try to keep the trigger methods and the general theme the same so the party can learn from their experiences.
10: Replace magic items that don’t have an explicit purpose in the module with more interesting or exciting ones, especially ones that will have an impact on this – or the next! – adventure. Same with very basic monsters, changing “goblins” to “blue goblins who are pottery experts and can squeeze through tight spaces like an ooze and take half damage from blunt weapons because they have cartilage instead of bones”. If there are bandits, give each band a name and a gimmick – the Merry Men give to the poor, the Compassionates never slay prisoners and use nonlethal weapons, the Rivals are always trying to one-up the other bandits.
At this point your module is coked up with some weird shit and you know it inside and out. Now is the time to trim it down.
11: Replace special rules with things that are already in the books, but only if it’s an exact match. If there’s a special table with % chances for escaping the pursuer, but your game already has it, just write the simpler rule in the margin so you don’t have to look it up. If the monster has a funky method for determining if it will flee, use a morale roll instead. This is definitely a place where you can make the game run smoother, but it’s also a place where you can accidentally lose some quirky charm in the module.
12: Can you find places where you need to roll all the time and replace it with some other method? Can you come up with a simple rule instead of a big chart to track things? You’re trying to reduce your overhead at the table. But this is also a place where you could lose something cool in the module.
By this point you’ve altered the module so much it’s possible a player wouldn’t recognize it. There is something to be said for running a module straight, unaltered, so that players across generations have a shared experience. But sometimes that experience is not so great, and sometimes the module is little-known so there isn’t much historical value. Make sure as you change things that you’re learning why the designer did it in the first place. Frequently something inexplicable is just misunderstood. You’re now deep enough in the module to figure that stuff out.
While running the module, continue to make notes. You should be able to start a game session knowing where you ended last, what timers are ticking down, and what the party was planning to do next. Keep track of player HP and such if they end in mid-dungeon just in case they lost their notes.
When you complete the module, look through to find any loose threads you can weave into the next adventure.
In summary, we have three phases of module preparation. First you read it and make margin notes to improve flow. Second you analyze it and look for connections and weak spots. Third you “improve” it by adding and removing as necessary. Each step is dependent on the previous and you can stop anytime and just play. For new DMs I would definitely suggest just going through the first phase and see what happens.