

Take a vaguely medieval world.
Add a problem, something more or less ecological, and a prophecy for solving it.
Introduce one villain with no particular characteristics except a nearly all-powerful badness.
Give him or her a convenient blind spot.
Pour in enough mythological creatures and nonhuman races to fill out a number of secondary episodes: fighting a dragon, riding a winged horse, stopping overnight with the elves (who really should organize themselves into a bed-and-breakfast association).
To the above mixture add one naive and ordinary hero who will prove to be the prophesied savior.
Give him a comic sidekick and a wise old advisor who can rescue him from time to time and explain the plot.
Keep stirring until the whole thing congeals.
--- Atteberry, Brian. (1992). "Fantasy as Mode, Genre, Formula".