1. Specific well written detail- Be specific about what you want to say. Less is more, so find the right word or words to show detail. Stay away from ambiguous descriptions like suddenly, look, like, good. These words aren't giving you the biggest bang for your buck. (For more about words to avoid check out Grammar Guru: Words to Avoid.) Also go a little deeper and use sensory detail. The use of sensory detail detail is a key element in good description. Try to use all when writing; sight, sound, smell, touch and taste.
Note: Do not rely too heavily on sight itself, instead try to use some of the other four for variety and depth.
2. Revelation of the characters inner life- A story will be more balanced and descriptive of the characters if their inner life or struggle is depicted. Go inside your character's "head" and show the reader what's going on, what thoughts are going on.
Note: When choosing whose point of view to write in, remember that describing something from a certain character's point of view can change the whole feel of a story. Figure out who will make the story more lively and entertaining to read.
3. Motivation, the impulse that drives the character- Motivation is essential to convincing the reader that they should care about your character. It is when you can reach out to the reader and show them what lies beneath.
Want to be more descriptive? Look around you at the people, places, and things in a new way. Notice not just the obvious details, but the less obvious, subconscious details. Keep a notebook of the things that stand out and you'll be amazed at how your new look at the world will reshape the way you write.
Check out the next 2 parts of this series...Description Part 2: 6 Pitfalls of Description
Description Part 3: The Secret to Good Description