Q: When I first introduce a character into a story, must I always give his or her last name? Is the first name enough? Must I name the character at all, or can I just refer to her as “our hero” or by her function (“…then the executive walks up to her boss and begins to…”)
A: Names of characters in stories are like the names of acquaintances in real life – the better we get to know them, the more important it is we know their names.
In a speech, presentation or marketing tool, identifying the hero of your story by his or her first name is sufficient, unless the story is about a famous person, or about someone you are purposely acknowledging as a courageous example or as the source of valuable information.
In screenplays, the major characters should all be introduced by their full names (all in UPPER CASE the first time we see them). From then on, you should consistently refer to them by either their first name only, or their last name only, both in the action, and above their dialogue. But minor characters, or those whose identities you are purposely keeping secret to create curiosity and mystery, can be called by their function or some visual clue you’ve revealed in the action, e.g. COP, TODDLER, TATTOO or MASKED MAN.
Novelists should almost always introduce recurring characters by their full names, and from then on by just their first names.