The definite and indefinite articles are two of the most popular words in the English language. They seem so simple: the is definite, a (or an) is indefinite. However, there’s a rule of writing that hides in their definitions.
a/an: used before a noun to generalize
With few exceptions, a reader must know a noun exists before the writer can use a definite article. This doesn’t mean the reader has to be aware of, say, spoons in general, but rather the spoon in a story must be introduced with an indefinite article before the writer can use a definite article.
For example: Sasha baked the cake can leave the reader wondering, cake? What cake? Since when is there a cake? Our job as writers – especially in a society with many other entertainment options – is to make it easy for our readers to follow the story.
A good rule of thumb is to think of your story as a trial, with your readers in the jury box. Before they can review photographs, clothing, documents, and records, these items must be entered into evidence. The first time you mention a noun, use an indefinite article (or personal pronoun). Thereafter, use the definite article. Easy, right?