J.K. Rowling introduces us to Hermione in Harry Potter and the Sorcerer's Stone when she's just beginning her studies at Hogwarts at 11 years old, but before classes even begin she's arguably the brightest student of the school. Hermione shows her strengths and character right off the bat in the first book of the series by taking the blame for her friends, being levelheaded in the face of danger, and using her expansive knowledge to get out of tight spots.
Quoted: "Books! And cleverness! There are more important things — friendship and bravery."