When writing your story, you should start with the basic questions:
Who-It's obvious, yes. But if you're thinking about building a world of your own design, you have to ask who are your characters. What do they do for a living? Whom do they have contact with? Highly recommended.
What-In terms of plotting the story, you have to ask yourself what the whole story is about. If you look at the foreign film En La Cama, you see the plot being about two strangers engaging in a one-night stand which becomes something more intimate.
Where-Location, location. This is the essential aspect to the story, in my opinion. A fictional setting can go in many different ways. Futuristic utopia, medieval fantasy, or a noir period. Now to bring the "who" aspect of worldbuilding to center stage, this is where it comes in. Your characters populate the world. Keep in mind that when giving the world you created whatever rules you have in mind, it has to maintain an equal level of reality too.
How-Another essential factor in creating your story setting is to ask how does it work. You got your population, governing body, limitation of resources, and so forth. What's key about it is to get an idea of how your world works for your characters, like say, how they interact with one another or where do they draw their source of energy for the whatchimacallit powering the city.
However you plot your story, remember to ask yourself the basic questions "who", "what" "where" and "how."