1. Some will know by hearing. You may be among those who will know simply by listening to what the book teaches. The Book of Mormon tells of thousands who heard the sons of Mosiah teach the gospel of Jesus Christ and "were converted unto the Lord" (see Alma 23:5–6). Missionaries today teach that same gospel found in the Book of Mormon. Some will know the Book of Mormon is the word of God simply by hearing others share its teachings.
2. Some will know by reading. You may be among those who will know simply by reading the Book of Mormon with a real desire to know the truth. Such was the case with my wife. She was 12 years old when she took to heart the instruction to read the book from cover to cover. As she did this, she knew it was true. The feeling was so strong that, as she read, she decided to follow the Savior forever. She has remained true to what she felt.
3. Some will know by doing. You may be among those who will know simply by doing the things the book teaches. Some people gain their testimonies by doing (see 1 Nephi 19:23; emphasis added). By likening, or applying, the teachings of the Book of Mormon in your own life, you may also become persuaded of its divine origin.
4. Some will know by asking God. You may be among those who will know by reading from the Book of Mormon and then asking Heavenly Father in prayer whether the book is true. This is what I experienced. It is the sublime promise extended by another Book of Mormon prophet, Moroni, to all sincere seekers of truth: "Behold, I would exhort you that when ye shall read these things … that ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost" (Moroni 10:3–4). I bear witness that if you read and pray about the Book of Mormon, following the directions of Moroni, you will know that it is true.