I want to share what I think is the most important thing in preparing to serve a mission. Read the Book of Mormon every day and every night get down on your needs and pray to know if it is true. One of the biggest things you will be doing is testifying to the people that the Book of Mormon is true and asking them to read it and to pray about it.
You need to have your own testimony. After you have gotten a testimony, study that book to know how to help other people know about the Book of Mormon. This book answers the questions of the soul. Your investigators will have many doubts and questions about this gospel. If Joseph smith was a prophet; if the word of wisdom really is a commandment from God; etc. Lots of doubts but in reality they only need to answer one simple question. Is the Book of Mormon true? Because if it’s true, then everything that we teach is true.
I testify that if you want success in your mission and in life you need to be constantly studying this book. I know now more than ever that it is true. Read it. And ask your Father in Heaven if it is true. Then prepare to share that testimony with the world.