Memorable characters come alive for us while we read. They live on the page and in our hearts and minds. We cannot forget them.
Be alert to characters you read about in the same way you are when you meet someone. Observe their actions. Listen closely to what they say and how they say it. Notice how they relate to other characters and how other characters respond to them. Look for clues as to their purpose and significance in the story.
Think about a major character in a story. Choose a very significant part of her personality and imagine the opposite of it. For example, if she’s rich, make her poor; if she’s old, make her young; if she’s happy, make her sad, and so on. How does this change influence the story and your view of it? Why did the author make the choice she did?