For me, the first major issue I come across is figuring out what the hell is going on in my story. I do plan the plot out before-hand, because it saves me from having to do four first drafts, but my planning is more like:
Needs to establish relationship and find out about Otherkind.
So there's no character notes, no description, nothing. I know where the plot is going, but not much else. For me, the first draft if figuring out secondary characters, scenery, dialogue, emotions - the tendons and muscles that go on the bones of plot.
As the story progresses, it gets easier, because I'm using the same characters, or similar scenerary, so I don't have to go and invent everything. I know what everything looks like, and how everyone acts.
Inevitably I end up writing an awful lot of drivel, just so I can figure out what the hell is going on.
And the second draft, for me, is condensing all this knowledge down into moments and flashes.
The human brain is a remarkable thing. Perhaps you've see the chain email or text, where all the letters are rearranged except the first and last letters of each word. You can still read the paragraph - your mind fills in the blanks.
To me, a writers job is to give that first and last letter to the readers. You need to give the reader flashes and moments that their brain can take and extend. This may seem like it's less work for you, but it's not. Because when you write half a page of description, you're conveying facts. And people can't make up facts, so you have to cover them all.
When you describe in flashes, you're conveying mood and emotion. That mood is tacked onto a couple of facts, and the reader is able to fill that description with all the images they have associated with that mood.
One example I have was when I was describing the neighbourhood that my main character grew up in. I described a train ride through the city, the slums, the houses, the way the roads went. That was fine when I was writing it for me.
The second time round, I described the train station - a hunk of concrete sitting in the middle of the rubble of last year's houses. I described that the dirt-track roads, with the occasional brick lain down - testament to a fools attempt to civilise the area. I described the rotting carcass of a dog, which underneath the preparation area for a street vendor who sold street food.
These are details that show you things. They show you the area is run down, hobbled together, a place that has lost a great deal of it's hope. A place where people don't care about food poisoning, because they're probably going to die of starvation in a week anyway.
Those descriptions took up a paragraph when clumped together. But it took time to think them up. I had to sit down and write a list of what I needed to convey about this place to my readers. Facts, mood and emotion had to be conveyed in a couple of details.
It takes time, but it's well worth it. So when you've written down the facts of your world, contemporary or otherwise, go back and look for the mood and emotion. Look for the facts you need to convey. Combining them in details gives the reader flashes of your world that they can extend. This makes for readers involved in creating your world - and there's nothing better than that level of involvement.