Dr. Mary Barbera highlights three common mistakes with teaching pronouns: introducing pronouns too early, using turn-taking pronouns like “my turn” and “your turn” with minimal language skills, and starting with receptive pronouns instead of expressive ones. She provides strategies to avoid these pitfalls, focusing on building vocabulary first, using simple language, and starting with expressive pronouns. By following these steps, children can effectively learn pronouns without confusion or pronoun reversals.