This is an expanded version of an earlier post.
Where is the near future and how does it work?
World-building doesn’t just apply to exo-planets and fantasy worlds. Science fiction takes place in a social and political context, and if a book doesn’t reflect that, then it’s more or less the equivalent of talking heads, where conversations take place as if the speakers are isolated in their own little world.
Where does the story take place? It can exist on a broad canvas or in an intimate space, but it must be located somewhere.
How did the world as you present it get to be the way it is? Or do you dump readers into the action and assume they’ll have no interest in how the characters got into their current situation?
Is there a larger picture, outside of the main story, but affecting it in some way? Most current science fiction, unless it’s apocalyptic, or space opera, ignores factors like global warming and assumes that technology will continue to develop and will be widely available, more or less as it is now. The side effects of overpopulation aren’t factored in, and neither are a lot of elements that have to be taken into consideration if the world is to give us the feeling that it could be real.
The real world is complex. Near-future science fiction should reflect that. Out of that complexity, you have to select what is necessary to the world you’re creating. Too many details and readers will be overloaded; too few and the world will feel like a half-built stage set.