Alot of good gamemasters stars to tell a story without having the proper planning, where the story goes great it oftens never finishes or the ending is as anti climatic as the story was great. Follow these 5 small advices to get some fast planning done and improve your overall storytelling.

Get an idea

You cannot plan an adventure without knowing what story you want to tell, you need to make an adventure, a story that can be what ever you like it to be, but keep in mind that it have to be something interesting to your players. Try and discuss with your payers what kind of game they like to play.

Is it hack and slash, is it sim games, is it mission based, or maybe a chase? There is many categories you can write an adventure in, in this place in the planning you need to figure out what.

Example (Idea)

Lets do one of my favorite chases. The group is captured in a dungeon, in an incredible cliche evil empire.

They have to escape the dungeon and escape the evil "mage, overlord, dictator".

Write the end of the story

Now that you got an idea of what the story is about, write the ending - mind that even though you write an ending it should be written on paper not carved in stone.

You need to set your destination before you head out, that way it is easier to know where to go, since you are moving towards a goal and not an infinite number of posibilities

This makes it is easier to focus, and you know when you are finished.

As you move along, you will find more plausible outcomes, just add it to the list.

Example (End of the story)

The group of adventures are now out in the free open world Where they will be met by a member of the  rebellion. He is giving them a horse and enough food to reach the rebel camp, and is sending them off in a hurry while he returns to his duties as a guard for the evil "mage, overlord, dictator"

Example of Plausible alternate outcome: The adventures enters the city from the dungeon without meeting the rebel contact, and are now escaping prisoners, who have to find a way to leave the city.

Define the challenges you want the adventures to overcome

Make a list describing the challenges you want, Is it an epic battle with 200 people charging eachother.

Is it recovering an item from an ancient grave, where the challenge is to get the item without angering the dead.

Or is it a long jurney, this list makes it easier to figure out what rules to pre read and include in the scenario, if a challenge is a snowstorm, you want to readup or include rules for how cold and stormy weather is working in your setting.

Example (Challenges)

Since this is an underground dungeon-dungeon.

  • Starting with litterally nothing and working their way up.
  • Sneaking / Breaking and entering (escaping) /Seducing.
  • Jailbreak
  • Recover maybe items that were aken upon arrest.

Make points of interest

Write a disposition, a bullet list of whats going to happen in the adventure.

Remember to keep to the main path and do not make too many branches, a good gamemaster should be able to improvise when the party moves out from the main story and either guide the players back on track or go with it. You can also make every point in a circle on a paper and then connect with arrows the flow of time.

The dots helps with what to describe later and writes a list of events. If a dot is a city describe the city or atleast the interesting part of the city, is a dot, a temple in the dessert, describe the dessert shortly and the temple in more details.

Chop it up

Now you can start chopping it in to smaller parts. In the city, whats going on there? Is there a group of thugs that is an encounter, in the wilderness will ghe group meet a travleling merchant goblin, they might want to assult unjustified just because of race? Or do they meet a cult or friendly priest in the temple that either supplies them with weapons from the dead corpses or blessings.

If you want from here you can divinde it in to smaller and smaller parts depending on how much details you perfere your self.