A lot of beginning writers, when they use description, might write something like this:
Tracy Smith, a pretty girl of 18, was five foot seven with a trim hourglass figure. She had red hair reaching a few inches past her shoulders and blue eyes. Her pale skin was dotted with freckles.
The writer seems to be just listing traits: name, age, height, hair, eyes, etc... We do get a picture of Tracy in our minds, but compare that example to this one:
Tracy Smith had the kind of eyes you couldn't stop looking at: a rare bright blue that shined and corralled your attention to her. Whenever the varsity tennis team was playing at home, there were always at least a few boys there to watch her lean figure serving and hitting the ball in her short white skirt.
Notice how much more information we get in about the same amount of space. In the first example, we have the written equivalent of a mug shot, but in the second we learn exactly how Tracy is pretty, how she got that trim hourglass figure. We get a much more specific sense of her—we know what distinguishes her from all the other pretty 18 year-old blue-eyed redheads. The information is more meaningful to the reader.
When you write, you want to question every word and ask yourself: "What work is this doing?" The best parts of your story will be doing the most work by serving multiple functions. They will not only describe the concrete physical surface, but hint at other facts, judgments, and ideas. You want to make abstract words like "pretty" more specific, and you don't want empty detail. Someone once said about writing: "If there's a gun in the room, use it." Don't just list the characteristics of the room, use those characteristics as keys to the inhabitant's personality, foreshadowing, symbols, or part of the action of the plot.
Practice using significant detail to describe a room. As we just discussed, you're not going to just simply describe the room, but make your description suggest more than what's on the surface.
Once you complete this exercise, you can get a critiquefrom a writing teacher.