GMing is not an easy task. It entails managing a lot of moving parts: the rules, the NPCs, a clear sense of the current events in the game, etc. When I sit down and talk to players who are afraid to become GMs, or new GMs who find the task daunting, however, I find the majority of them cite the creative demands running the game as the most intimidating. Coming up with ideas for worlds, NPCs, and adventures. Nervous GMs often worry the most about where to get ideas.
Most reluctant GMs look at the blank campaign notebook before them and then say to themselves "I don't have enough ideas to make this work." They assume that you need a lot of ideas to make a TTRPG campaign work. Some believe that they need a plot or a complex and fully-realized world.
All a campaign needs is two or three good ideas. Because when you have just a few good ideas to build a scaffold for a campaign, they serve to generate more ideas. The first region in your campaign world, your setting, and your first adventure are the spark that will create more ideas of their own accord once you start playing.
The job of a GM isn't to have a notebook stuffed with ideas and notes to sustain a campaign. It is to create a few good "idea generators" and let these do the hard work the group starts playing. A good campaign quickly becomes self-perpetuating, and the GM will find that the creative work practically does itself.
So, What is an Idea Generator?
An idea generator is a few good ideas linked together that will inspire the GM to offer hooks to the PCs, or will give the PCs reasons to explore the campaign world of their own volition. They can be any kind of fact, Content, or character in your world. Generally, the moment they appear during play, the PCs start reacting to them in a way that creates opportunities for new ideas to emerge.
Some great examples from established D&D products of idea generators might include: