In order to select quotes for analysis, you must first know what you are analyzing. What is the question you would like to explore? What parts of the book are you most interested in? These are essential questions that you must answer in order to do an in depth analysis. Otherwise, you're simply choosing a quote at random and discussing it. If you don't have an angle from which to work, it is impossible to analyze something in depth.
That being said, there are so many topics from which to choose in any book. In The Kite Runner, you could choose guilt, discrimination, or redemption for instance. Choose a topic to start with and then you can be successful in choosing quotes to analyze.
Enotes has some very good examples of themes. There are links posted below for your further consideration. There are essential passages to work with. Use them as examples to help you get started on your own analysis.