It’s a generally-accepted truism that what makes for good, effective description is a combination of careful observation and a keen eye for the telling details.
What isn’t said so often is that you have to be careful which telling details you pick to use, and when you decide to use them. Your readers have years of training in the grammar of fiction, both popular and literary. They know quite well that some details have an extra job to do, and some of those jobs are hallowed by tradition.
For example: In the real world, anybody can have a cough. But in the world of fiction, things are different. If the coughing character is lucky, all that a cough will do is alert somebody to his or her presence when that presence ought to remain unknown. Characters in long or arc-based fictional formats have no such good fortune, however; for them, a cough almost always foreshadows a lingering and probably fatal illness within the next few chapters or episodes.
Similarly, people in the real world have occasional disagreements and even sharp words with their nearest and dearest without having the entire relationship fall apart as a result. In fiction, even a mild exchange of the “I thought you had the car keys!” variety tends to become the harbinger of breakups to come. (This may be why the obligatory “this is a happy family” scene that precedes so many disasters in film and television tends to be so sappily anodyne – anything else would be over-interpreted by the audience.)
A full catalog of all the possible traditional telling details would take more time and space than I have here. All I can say is, keep an eye on what you’re showing the reader, and make certain you’re not accidentally foreshadowing things that aren’t going to happen.
Dr. Doyle's Blog 