Elder Holland gave this talk at the MTC in 2011.  In this talk Elder Holland discusses the goal behind the development of Preach My Gospel.  I think it's really important for prospective missionaries to understand its purpose, which is multi-layered.  First it is to enable missionaries to follow the Spirit and share what they are prompted to teach.  Second, it is meant to strengthen and convert the missionary teaching the gospel.  As we listen to those we teach and love them the way the Lord loves them, the Spirit will prompt us to know what to share with them and how to answer their questions and concerns.  There are so many excellent nuggets in this talk for prospective missionaries.  Listen to this talk with a pen and paper to write down what the Lord is trying to teach you.