You're creating a world. You want to write a story in it, and you want it to feel real. How best do you go about that?
Well, you have to have all the underlying basic principles down. Climate, ecology, economy, etc, etc, etc. It all has to fit together and make sense. But a lot of that stuff isn't precisely relevant to your plot. The temptation might be to explain things - and that leads you into trouble. You want people to believe in you, yes. But don't tell them things and ask them to believe. If you show those things effectively, then they'll believe in spite of themselves.
I'm sure you've all heard this "show don't tell" advice before. I have a whole post on its different meanings, but I'm not trying to access all those meanings today. I just want to say that if you can bring your worldbuilding efforts into sharp focus, you can achieve that "show don't tell" feeling, and a little bit of worldbuilding can go a long way.
A good place to start explaining this is with a short story. Say your story is short, so you don't have room to try to explain the world - and yet, you want to make sure that the world feels large. One really good way of doing this is picking a single object to start with. This object has to be one that has high relevance to the character - but not necessarily to the plot. I recommend everyday objects. Not something like a fork which has become nearly generic, but something that is slightly off what in the real world we would consider normal. Maybe it's a ceremonial object, or an object of significance to the main character. Maybe it's this Roman "Swiss army knife" that Astrid Bear pointed out to me on Facebook this morning (thank you!).
The reason why I enjoyed the Roman knife-tool was that it was so detailed. So much to be learned from its discovery about the habits of the person who carried it. The fork and spoon. The blade. The spike which may have been used to remove the meat from snails. The toothpick; the spatula.
If you can pick one highly relevant, salient object, its nature can imply many things about the world around it. In my story, "Let the Word Take Me," (Analog July/Aug 2008) I gave my alien girl two objects like that - a ceremonial knife, and "sun armor." Here's a quote:
On top [in the artifact case] was a ceremonial knife in a scabbard of intricately worked grazer-leather, with a leaf-shaped blade and a hilt wound with stone beads. Underneath was a mass of white feathers. Lifting the top layer, he found himself unfolding a hooded coat of perforated leather densely clad with yorro plumage. ... David suspected it was an heirloom; the unblemished feathers were layered without gaps, but the leather inside showed that patches had been resewn, and two of the worn tie-thongs had been replaced.
I spent this many words describing the two objects because of what they said about the technology level and culture of the people who had made them. Find the right object, and its significance will radiate outward, accomplishing far more than general descriptions on a larger scale.
The fact of the matter is, while this technique is very convenient in short stories where you have fewer words to work with, it is equally effective for longer works. The objects don't have to be ceremonial or have special importance. They can be small things that the characters consider quite mundane. A lot of large-scale principles become evident in the tiny details of the everyday. Focus your worldbuilding efforts and you can get a lot of power out of a very few words.
It's something to think about.