There are two different methods that I use to design adventures, and it depends upon what the focus of the group is. If the group is mostly focused on combat and skill encounters (traps, tracking, etc.), I tend to make a site-oriented adventure (read: "dungeon", even if the "dungeon" is a forest or a city instead of an underground warren). If the group is mostly social interaction based ("I want to run a __ [thieves' guild, fighting school, church, kingdom, etc.]"), then I tend to use a plot-oriented adventure. That's not to say that there isn't overlap between the two; often, I'll include a small dungeon in the plot-oriented adventure or a series of plot threads to follow in a site-oriented adventure.
Method 1: Site-Oriented Adventure Design
Here, I tend to put together a limited-access site that contains between six and ten combat encounters, fifty to eighty percent of which have CRs within two levels of the party's average ECL (note that this may not be their actual mean level; I eyeball this, because my players tend to be
very good at creating effective characters), five to fifteen percent of which have CRs more than two levels below the party's average ECL, and ten to twenty-five percent of which have CRs more than two levels above the party's average ECL. Usually, these encounters will have a theme for the most part (the elven tomb will have a lot of undead, for example, with a few staple constructs or aberrations included).
In addition to the combat encounters, I tend to include between four and six character-appropriate skill encounters (traps for the rogue to disarm, parties to track for the ranger or barbarian, areas that require the fighter or the monk to climb to, arcane runes for the wizard to decipher, etc.). Even if no one has disable device as a skill, it is worth putting in a few "puzzle" traps for the party to work through; they can get clues from their knowledge skills or perception checks (really, anything that you can think of; the point here is to let each player feel as if his or her character is doing something to contribute). I hand out xp for these just like combat encounters, so that the party feels as if they achieved something.
The "boss encounter" is a staple of this sort of adventure design. Usually, it will occur in the most inaccessible portion of the dungeon, be it the dark grove at the heart of the woods or the burial tomb at the bottom level of the necropolis. However, sometimes it's worth putting this at the very beginning and sticking something that the PCs will want to get to in the most inaccessible portion of the dungeon (for example, have the adult green dragon that haunts these woods see and attack the party at the edge of the forest, just like everyone else; it then becomes the adventure to find the dragon's horde before someone else does and loots it). It makes for an interesting twist.
Method 2: Plot-Oriented Design
For these types of adventures, I usually sit down and write a flowchart of NPC motives and possible outcomes. For each of the major NPCs, I write a blurb of three to five motives that they have (for example, the burgomeister running the small city of Ascii has two major goals of: 1.)keeping the line of trade with Pondside open, and 2.)ensuring that the theives' guild receives their cut to avoid open street warfare; and three minor goals of: 1.)ensuring that his daughter doesn't marry the good-for-nothing bard who is involved with the theives' guild without the burgomeister's knowledge, 2.)getting rid of the persistent illness that causes his rasping cough, and 3.)ensuring that his cousin's shipping business continues to flourish at the expense of the thieves' guild's efforts). I then try to sit down and think about possible PC actions at each of the nexus points that information is revealed to them (and who is doing the revealing, be it NPC interaction, knowledge skills, running across an ancient tome in a dungeon, etc.), and chart the NPC reactions that will flow from that.
XP awards in this sort of adventure are more ad-hoc on my part, with major awards being given when the PCs achieve primary, secondary, and tertiary objectives, normal awards when they only achieve two of the three, and minor awards when they only achieve a single objective. The objectives vary dependent upon the PCs motivations.
This sort of adventure is more difficult to run, but can be very memorable when done right.
Edit:
As far as my actual structure for adventure
notes goes (a different matter than the actual design of the adventure), it also depends upon the adventure type.
For a site-oriented adventure, the dungeon map is essential to me. I draw up a map of the site and a key for the map (note that the key is probably going to be between ten and twenty pages in length) that includes all of the essential encounter information for the adventure. Some of the time, I put the combat encounter information in a separate document for brevity (I tend to use a lot of the same sort of monsters in any given dungeon, so there's a lot of overlap between separate combats); however, I find that this tends to lead to "note bloat" and difficulties in finding the information that I need readily and easily. As we go along, I make sure to draw up the dungeon on a wet-erase map while one of my players maps it on graph paper.
For a plot-oriented adventure, I keep copious (
COPIOUS, I say![/badJohnCleeseimpression]) notes on the major NPCs and plot points. Here, there is the main flowchart of possible interactions and dossiers on each of the major NPCs, groups, and challenges that will occur in the adventure. My note block for a single major NPC usually runs to about a page of 12-pt font, organized in bullet list format (this allows me to prioritize their motivations and reactions according to likelihood of occurance, NPC priority, and likely interactions). The flowchart for the whole adventure (assuming that the adventure will bring the PCs to their next level, on average) usually runs to about four to six pages, handwritten. I also keep a list of random names and physical/personality traits handy (you never want to have the PCs talking to Stable Hand
#4 it's much better to have him be Harod Leuthwait, the Baron of Grosling's key stablehand who has a daughter that he is trying to marry off to a local businessman and a limp from when he was a boy and fell out of a tree). I also keep a list of random names for places and things, just in case the PCs run off somewhere weird on me.
It winds up being quite a bit of notes, and organization here is key. I ensure that everything is divided up first by subject (monsters, NPCs, plot points, random names, places, etc.) and then alphabetically (since this is the easiest way for me to keep track of it) either in a binder or on my hard drive. It sounds like a lot of work, but once you get a feel for the campaign world's base assumptions on politics, religion, race, combat, environment, and magic, the rest of it should fall into place rather easily. It's just a matter of keeping your notes organized so that you can remember that the third daughter of the baron is really courting a wererat who is part of the thieves' guild, because if you gave that hint to your PCs, it
will come up at some point.