Dungeons And Dragons: How To Create The Perfect One Shot
1. Shock The System
One-Shots are a unique beast. They go against the very nature of Dungeons and Dragons, which is designed to be a long-form narrative collaborative play. While that may be the case, that doesn't necessarily mean it's a bad thing.
The first thing a Dungeon Master and their players should ask is why they are choosing to deviate from the original play style they've established. One-shots, as previously stated, are a chance to have fun, be fearless, take chances.
If your traditional game is full of political intrigue, make the one-shot about bumbling orcs. If it's a lighthearted romp, go for a gothic setting with horror undertones. Similarly, players who are used to memorizing dozens of spell mechanics may enjoy the chance to turn their brains off and become barbarians. A player who exists in a support role may be forced to step up as the face of the party.
This gives everyone at the table a chance to enjoy some new tactics, new combinations, and new settings. At worst, it may reinforce the things everyone already enjoys. On the flip side, it may result in some surprising discoveries at for your group not just about the characters, but the players themselves.