In this writeup, I’ll discuss the principles I’ve learned in my years of GMing Advanced Dungeons and Dragons 2nd Edition, Alternity, Cyberpunk 2020, and Violence: The Role-playing Game of Egregious and Repulsive Bloodshed.

Adventure Hooks
Obviously, adventures are worthless unless you can get the players involved. The hook can be anything designed to pique the player’s interest, from the tried-and-true “A man walks up to you in a bar” and “You see a sign reading “Adventurers Wanted!”” to something far more complex. The hook for the excellent Alternity adventure The Killing Jar was the theft of a player character’s car and its subsequent discovery by a West Virginia towing company, a simple beginning which drew the characters into a web of conspiracy involving unscrupulous pharmaceutical companies, the Mothman, and alien life forms from the depths of the earth.

Plot structure
When planning your adventure, there are three main factors to take into account: space, time, and character. These three can be combined in any way, with the best adventures integrating all of them.

Spatial structure
A purely spatial adventure is very easy to design, since all you really need to create is a setting. The basic dungeon crawl is a good example of a purely spatial adventure, stripped of all the niceties of plotting and characterization. Time, too, matters little, since that umber hulk will be in room 17 of level 4 whether the characters enter it tomorrow or if they explore it after 10 years of game time have passed.

Designing the space of your adventure is fairly easy, but there are a few things to remember. When planning an environment in which the characters will spend a great deal of time, be sure you’ve covered all the relevant details, as it’s incredibly irritating when the GM is reduced to odd hand gestures in trying to describe a scene. Draw a map.

Likewise, when designing a space in which the characters aren’t likely to linger, you can be vague on the details. It really isn’t necessary to map the location of every rest stop along a highway or every tree and clearing in a forest unless you have some encounter planned there.

The advantages of pure spatial adventures are many: they’re easy to design, easy to run, and aren’t likely to surprise the GM with their outcome. The disadvantage lies in their shallowness, since they don’t have much room for variation and complexity.

Temporal structure
To make your adventure more interesting, you’ll need more than just an environment. Adding the element of time allows for greater depth while sacrificing some of the flexibility of a pure spatial adventure. Integrating time into the fabric of your adventure takes serious work. You’ll need to plot a timeline of the significant events, taking into account how the actions of a character in one scene might hasten or delay another. A character who is badly mauled early in the adventure will have to spend a significant amount of time resting and healing if he doesn’t have access to magical or high-tech healing, and consequently might not be available for later scenes. Timing can also have significant effects on the environment. For example, a local volcano might be on the verge of erupting and burying a site that contains a clue or an item significant to the plot.

Planning time is difficult and complex, as no GM can foresee every possible outcome of a scene. I can only advise you to be flexible, prepare to have some of your scenes invalidated by the actions of your players, and don’t beat them over the head with your plot hammer. You risk hurled dice bags or worse when the villain around whom you had planned a major scene manages to escape despite being gagged, hog-tied, locked in a steel chest, and guarded 24/7.

In all the RPGs I’ve GMed, it’s been impossible to design a purely temporal adventure, since characters have always been spatial creatures inhabiting a spatial environment. Time is more of a secondary element added the primary factors of space and character.

Character structure
Ah yes. The most difficult and consequently most neglected part of good adventure design. Once you’ve mastered this, you’ll have all the elements needed for a truly memorable gaming session.

Consider the major characters and groups involved. They’re going to be the driving force behind the adventure. Design your major non-player characters in depth. The Complete Book of Villains provides a handy blueprint. Try to answer the following questions.

What are they trying to accomplish? This can be anything, but it should be realistic and believable. Madmen trying to subjugate the world and personal grudges against the player characters will only take you so far. Try to create complexities and shades of gray. Think about why the characters want what they want.

Why are they trying to accomplish it? Money and power are the two most common motivations, but it could be something else. Keep in mind those intangible things like respect, influence, and prestige that can drive people to extremes; Napoleon said he could make men die for pieces of ribbon. If your villain is human or humanoid, remember that evildoers always think they're doing good. If your villain is inhuman, you should understand its motivations, even if nobody in the campaign world does.

What can they use to achieve their goals? Do they have a horde of minions at their command? Do they have a strong influence over other powerful people? Are they skilled orators, able to command a crowd? Whatever you decide, don’t just create a single supremely powerful character and set him/her/it against your players, and remember that knowledge is the most powerful weapon of all.

Who opposes their agenda?Probably your players. However, to make things more interesting, you can add a second, third, or fourth interested party, each with its own goals and motivations, which may overlap or conflict, catching the players in a web of intrigue. This sort of thing works especially well in conspiracy games like Dark Matter.

Pure character-based adventures can be fun, but they lose something without the added dimensions of space and time. An adventure of courtly plotting and intrigue is a good example of a simple character-based design.

After you’ve designed your settings, plotted your timeline, and answered these questions, you’re ready to start writing the adventure. Write descriptions of the settings, write timelines of events, and write character sheets for your NPCs. Write down the important dialogue (you don’t want the evil overlord to be fumbling for words in his climactic speech). Write down anything you can think of.

Once you’ve written it all up, you’ll need to add some form of structure. I find that a flowchart of the action helps in plotting the likely courses of events and their consequences.

Visual Aids
Instead of just reading text to your players, create a realistic visual aid. For an ancient scroll, you can use kitchen parchment (or just scorch some regular paper) and a broad fountain pen. If your PCs discover pages torn out of a diary, rip some pages out of a blank book and write on them (add coffee stains for a little extra realism). Act out the posture and gestures of NPCs. All this takes time, but can immeasurably enhance the total gaming experience.

Know your players
Design encounters that give each player a chance to shine. Your thief may not be able to contribute much to fights, but he’ll feel special knowing that his lockpicking skills got the party into the villain’s inner sanctum.

Stay in character
Not all of your NPCs know everything you know. Make them behave accordingly, even if it means sending them to their deaths. Likewise, a player may know something vital that his character doesn’t. Be sure they separate this knowledge. Remember that gaming isn’t supposed to be a battle of wits between the players and the GM.

Remember: it’s only a game, and the point is to have fun. Don’t hold grudges or let your feelings towards each other spill over into the game.