A carpenter will use one set of tools to build a table and a larger set of tools to build a house. Similarly, your purpose should dictate which descriptive writing tools you use and how much description you provide. Base your purpose on what your readers already know, or need to know or might enjoy knowing.
Snap your words together like playful building blocks to fashion a castle. Use nouns to make your readers "see" your castle; use verbs to make them "feel" it. Select your words carefully to achieve the impression you want to convey. For example, call your castle a "palace" to suggest extravagance, a "fortress" to denote strength or a "relic" to underscore age. Describe how your castle towers, sprawls or creaks to give it personality. Adjectives and adverbs are sufficiently descriptive in a narrative, but for vivid imagery, you need to amplify them with detail. For example, instead of simply saying "We approached the formidable fortress that stood proudly in the distance," write "The fortress beckoned; the scars on its face mourning lost battles and its immense shadow commanding hush and awe as it touched you."
For factual, objective descriptions, use denotative language, which is straightforward, literal and unbiased. This language applies well to technical documents, such as equipment owner's manuals, and legal documents, such as a website's terms and conditions. For personal, subjective descriptions, use connotative language to stir an emotional response. Connotative language uses figures of speech such as similes, metaphors, hyperbole and personification to provide rich detail. For example, note how a metaphor and a simile enrich this description: "We beheld the fortress in the distance, a lone sentinel gleaming silver-gray in the midday sun, like a knight in full armor ready to battle but going nowhere."
Explain how your subject looked, sounded, smelled, tasted or felt. These sensory details control the image in your readers' minds and provoke their imagination. Listen to the echo of footsteps on a stone floor. Peer, squint and blink to comprehend the shape at the end of a dark hallway. Welcome the scent of gardenia in the suffocating mustiness of the dungeons below.
Impose structure on your descriptive writing piece to guard against a rambling litany of sensory detail and emotions. Begin with the overall impression that you want to impart and then use or discard details accordingly. Organize your material according to emphasis, sensory impression or your perspective in space and time. Use signal words such as "afterward," "ahead" or "below" to guide your readers.