In practice, the Shadowrun adventure templates always seemed to work for me as a model for games where the PCs aren't necessarily going to travel in a simple A-B-C progression through the plot. It works well for PCs who will be acting independently, following their own leads, investigating people and places at their own discretion. It generally feels pretty versatile, allowing for such free-roaming PC behavior while still maintaining a plot (rather than simply an "Explore The Hex" type oldschool AD&D module). On the down side, it requires the GM to really familiarize himself with it before running it; doing it cold means a lot of page-flipping and possible mistakes.Click here to read Mr. Parker's breakdown of the Shadowrun format.
On a more old school tip, here's David Cook explaining how the A series of modules for first edition AD&D were created (from the forward to the compiled A1-4 Scourge of the Slavelords megamodule):
What's interesting for our purposes is that even with the smaller stat blocks of yesteryear, the A series of modules clock in at around 30 pages each.
First, each designer chose a low-level monster that would be the basis for his round: orcs in A1, hobgoblins in A2, and gnolls in A3. Next we decided on the number and type of encounters that would occur: nine encounters to fit the time limit of 3 1/2 hours. We guessed this would give a good team just enough time to get through every encounter.
We also set what would happen in each encounter. Thus we came up with the following list:
1 Trick to fool the players
1 Problem the players had to solve
1 Encounter with the basic monster of the round (orcs, hobgoblins, gnolls, etc.)
1 Ambush prepared by the basic monster of the round
1 Encounter with the basic monster and a friend (an ogre, for example)
1 Encounter with an unintelligent monster
1 Encounter with a brand new monster
1 Grand Finale
Using this list, we each went to design our tournament rounds.