One of the first mistakes that a writer of speculative fiction (science fiction, fantasy, or supernatural horror) makes is front-loading every little bit of information of their world that they painstakingly made. One of the last mistakes that a writer of speculative fiction makes is giving stupid details of their world, unknowingly retconing things, and explaining things that don't need explaining because this usually ends their career or irreparably damages a franchise. Today's lesson is about "bad worldbuilding" because the hardest part of actually creating a fictional world is giving too much detail.
This one is going to be different for different types of media. For example, most television shows have a build-as-you-go kind of feel (think Fairly Odd Parents), while a series of novels is usually planned out from the beginning. As an aside, if you're planning out an entire series of novels, make sure that at least the very first one can stand completely on its own to the point where