Specify Garment and Material
There are many words for the same type of garment. A shirt can be a T-shirt, a polo shirt, a dress shirt, button-down, tank top, blouse, sweatshirt, sweater or cardigan, among other things. Each variation connotes something different about the character and story. T-shirts are associated with a certain casualness, while long-sleeve dress shirts are typically more formal. By specifying the make of the shirt, you’re drawing a more definite visual. Further identifying the material -- denim, twill, wool, cotton, tweed, polyester, corduroy, fleece, spandex, leather -- adds even more dimension. “He was wearing a shirt” is a vague statement compared to “He was wearing a spandex tank top.”
Describe Clothing Color
Nothing imparts a better visual impression than color. Vividly describing the colors of your character's clothing can enliven ordinary writing. “He was wearing a spandex tank top” is an improvement from just mentioning that your character’s wearing a shirt; but consider adding the element of color: “He was wearing a black-and-yellow-striped spandex tank top.” Figurative language, metaphors and similes can make the visual even more striking: “He looked like a strange, giant bumblebee in his black-and-yellow-striped spandex tank top.”
Show Style and Personality
As you begin layering clothing descriptions with more specificity, be conscious of what you’re revealing about style, historical setting and personality. Tightly laced bodices and flowing gowns may instantly put readers in medieval times or in Victorian England. Tie-dye shirts and bell-bottoms will likely orient readers in the 1960s. Use clothing style to reveal not only historical periods, but your character’s personality traits. If your protagonist is a laid-back Californian, he might wear tan cargo shorts and black flip-flops. If your protagonist is a wild, 20-something socialite, she might wear a short black dress and lipstick-red cowboy boots.
Reveal Class and Social Status
Perhaps more than any other feature, clothing can indicate social class. A character who wears a fine, woolen, navy-blue suit will appear different to readers than a character who wears baggy sweatpants and a blank white T-shirt. Decide what you want clothing to say about your characters and the environment in which they live. In “Crime and Punishment,” Fyodor Dostoyevsky uses clothing to expose ostentatious class differences in czarist Russia. The tattered suits of the impoverished student Raskolnikov are often likened to rags, whereas the well-to-do suitor Pyotr Petrovich carries around an “exquisite pair of lilac-colored, real" Jouvin gloves.