By engaging in conversation on this point, you will be inviting your friend (and committing yourself) to go deep below the surface of everyday trivialities into the heart of the matter: Why are we here? What is truth? Is there a right and wrong? Is there a God? Is there an afterlife? Is Jesus Christ God? Did he found a Church during his lifetime? If so, which one? Do we need to belong to it to be saved? Of course, you need to be not only willing to discuss and answer these queries, but also to be prepared to take on this task.
"Be ready always with an answer to everyone who asks a reason for the hope that is in you" (I Peter, 3:15). To be an evangelist in today’s world means to be an apologist. This is the work of a lifetime, but that does not excuse us from evangelizing while we learn on the job. Remember: no matter how little we know, our friends often know less. And what is more important, we know where to go for the answers.
A lot of our catechetical work with our potential convert friends will be, happily, simply to refer them to the best sources. Obviously we should have a good grasp of the New Testament and the Catechism of the Catholic Church, our fundamental texts. However we should also slowly but surely read and study the great English and American apologists: Newman, Lewis, Chesterton, Benson, and Knox, as well as more modern masters, Sheed and Kreeft. Many of their works are in print. It is also useful to be familiar with the magisterial teachings of the Pope for the most current teachings on matters of faith and morals.
Reviewing our own preparation leads directly to the question of recommending reading for friends who express an interest in our faith. An increasing number of people simply don’t understand the basic vocabulary of what it means to believe. Belief and Faith – an excellent and brief volume by the famous German philosopher, Josef Pieper – draws heavily on Cardinal Newman’s much more complex Grammar of Assent. Many people today need a book to awaken their interest in Christianity or a volume that helps to make Christianity "reasonable" and understandable. Several books come immediately to mind: both Orthodoxy and The Everlasting Man of G. K. Chesterton will stimulate the reader. Frank Sheed’s A Map of Life (Ignatius), and C. S. Lewis’ famous Mere Christianity also come to mind.
Most fundamental, of course, is the New Testament. An excellent version with commentary is The Navarre Bible (Scepter Publishers). And we might recommend a good Life of Christ (try Goodier, Sheen, Riccioti, Guardini). Your friends simply must come to know the life of Jesus Christ if they are going to be able to join His Church.
Second is a good Catholic catechism so that they may come to know the Church and her teachings. There are many excellent ones in print, by Frs. Trese, Hardon, Lawler, Noll, and others. Just choose one that you are comfortable with and one that reflects the sound teaching of the Church updated for the Second Vatican Council and the authoritative recent Catechism.
I would recommend that you whet their appetite for conversion by giving them a book or two on stories of conversions: Spiritual Journeys (Pauline Publications) or Surprised by Truth (Basilica Press) come immediately to mind. Our friends will be intrigued to read about the contemporary conversion stories of so many people drawn to the Faith from such varied backgrounds, and they are sure to find at least part of their story in one of these histories.
Don’t forget, either, the classic spiritual autobiographies of St. Augustine, John Henry Cardinal Newman, Thomas Merton and Malcolm Muggeridge, as well as the more recent story of Dr. Bernard Nathanson. They have changed millions of hearts and minds.