Concrete detail consists only of those details that you can see, hear, smell, taste or touch. If you are describing an apple, concrete details would include the fact that it is red, that it has a smooth skin, that it is round and that it tastes sweet. Abstractions, by contrast, are things that you cannot see, hear, smell, taste or touch. Examples of abstractions include “truth,” “sadness” and “honor.” Avoid abstractions in your concrete-detail essay.
Choose a subject that is interesting enough for you to be able to describe it concretely without repeating details or stretching for words. If you are writing a two-page essay, choosing a rubber ball for your subject probably wouldn’t work -- it is round, it feels springy, it smells like rubber, but there’s not much else to say about it. A library or a gym, on the other hand, would give you plenty of things to describe.
Describe the object, place or experience immediately, without framing it through the use of phrases such as “I see” or “I feel.” If you are presenting a visual detail, it is clear that you are seeing it -- the framing phrase wastes words, and pushes your reader away from what you are describing. Compare the mediated sentence “I see that the apple is red” to the stronger, unmediated sentence “The apple is red.” The second sentence presents the color of the apple in an immediate way, as though the reader is seeing it directly.
A related concept to that of concrete detail is specificity. Not all concrete details are specific. “Chair” is a concrete detail, but it is not specific. “Stool” and “recliner” are both more specific concrete details than chair. “Broken-down blue recliner with a salsa stain on the left armrest” is an even more specific detail. Use details that are as specific as possible when writing your concrete detail essay. The more specific your details are, the more clearly your readers will be able to visualize your subject.