One way to strengthen your writing voice is to make sure you are choosing strong, specific words. In particular, focus on strong nouns and verbs.
Be wary of adjectives, which are often vague and open to interpretation. To me, the term “young girl” suggests a child no more than six years old, but I’ve heard the phrase used to describe a woman in her early 20s. Factual details or clear comparisons are less open to interpretation, so be precise. For example, calling a character “big” isn’t specific. A man who appears average or even small to an adult might still appear big to a child. A Japanese man who is of above-average size in Japan might be smaller than average in Denmark.
If you want to create a clear picture, you can use specific statistics, such as saying that the man is 6’6” and 300 pounds (would that be fat or muscle, though?). Or you could use a familiar comparison. Perhaps he’s built like a pro football player (would that be a quarterback or a linebacker?). Keep your audience in mind. Will they be more familiar with a linebacker or a sumo wrestler?
Specifics are especially important when writing for children, as a child may have a very different idea of what constitutes big or small, young or old. To a kindergartner, a 40-year-old teacher is ancient!
You can even create mood by being careful with specific word choices. Say you have a woman wearing a red dress. If you describe the dress as blood red, it hints at danger. Scarlet and crimson suggest an edgy sexiness. Burgundy, ruby, or garnet evoke a sense of wealth and luxury. Cherry red is cheerful. Rose red is soft and gentle. You can use specific words to create a mood that suits that character, or that point in your story. Or you could mislead your reader, creating certain expectations through word choice and then challenging them with the character’s behavior.
Be specific with your verbs as well. As for adverbs, some writers recommend avoiding them whenever possible. Adverbs may, on rare occasion, have their place, but often they are a lazy alternative to the harder work of showing with strong verbs. If someone walked slowly, did he stroll, stumble, shuffle, or limp? Those are all slow ways of walking, but each looks different to a viewer and has different connotations.
Assignment: write a paragraph about a character or setting, being as specific as possible with your language.