There are many interpretative questions you can ask about this book. Here are a few:

What message is the book trying to portray?

What were the consequences of each person's response to finding the pearl?

How would you have reacted to sudden wealth like Juana and Kino's?

What does the story say about humanity at large?

How do free choice and fate play out in the novel? Do you think the novel's ending is inevitable (guided by fate), or could the characters have changed it with different choices?

Do you think Kino should have "kept his place"?

How could Kino and Juana have acted more reasonably in response to finding the pearl? Would it have led to a better outcome?

There are many other questions that can be asked, but you can use these as a guide to begin analyzing the text.

To name a few:

In what way is the story a simple folk tale, and in what way is it more universal?

Trace the relationship of Juana and Kino from the beginning to the end and how they evolve differently as the story develops.

Kino is punished for having betrayed an age-old law of "keeping one's place."  Discuss.

Identify and discuss the lyrical elements in "The Pearl" and how they enhance both the story line and the theme.

Trace the use of both light and sound as symbols throughout the story.

Identify and discuss the stock characters in "The Pearl"; as stereotypes what do they represent?

What is the tandem of fate and choice in this story, and what observations can be made from this duality?

Below are references you should find helpful as well.