That strange substance that fills in the gaps and trickles through to give depth to the story can be rewarding. Atmosphere is like a fine balancing act between giving enough detail, and too much that would detract from the story. I am guilty of not providing enough detail with my first draft. This is where it is helpful to know your weakness when writing.
It can be great to write down ideas as you think of them, yet this can little room for all those other bits. It is a learning process, and one that is good to get feedback on. It is easy for the writer to imagine the world as the story moves along. In addition there needs to be enough detail intertwined in the story to pull the reader along. Like little bread crumbs or corner stones that hold the picture together igniting the senses and the imagination.
Story telling is as much about creating an image as it is a journey, evoking memories of places, colours and smells, light and dark. The atmosphere assists with filling the reader with a believable world to step into from one page to the next. If you have spent a great deal of time creating the back story and world building this is where all the hard work can make a world of difference. This is not the time to go into massive detailed explanations which can remove the suspense and mystery from the story. Rather it has to do with enhancing the scenes and bringing them to life.
This is an area that I am still working on, much like a work in progress. Finding the elusive middle ground somewhere between the action sequence and the background. Where the journey and the experience are well grounded in the created world, yet the world remains part of the background. If there is too much background this can stall the story, yet it needs to be there in glimpses shining through and marking the way. Safe to say it is going to take me a while to get the hang of it, especially in the first draft. Thank goodness for editing.