Well, it's quite different from person to person. In my experience, I imagine places/people/voices I've seen in real life and movies and apply it to the story. Your whole life could affect how you see the story.
Who am I kidding just watch the live action version of the book lol.
When you want something to seem real you try to assiocate is with something that is already real therefore making it seem like that said something that is real making a story, place or person feel real. And all of those examples make a story seem more real.
