Hope this helps alittle. They all can be right by Steve Russo is a book that has a nice overview of Mormonism. Here's some exerpts under Key Differences between the Mormon Church and Christianity.
• Mormons teach that God the Father is a mere man with flesh and bones. Christians believe that God the Father is spirit and does not have a body of flesh and bones (John 4:24).
• Mormons claim they have received further revelation of biblical teaching in books like Pearl of Great Price, Doctrine and Covenants, and the Book of Mormon. The bible; makes it very clear that the Bible is the final Word and warns that nothing is to be taken away or added (Rev. 22:18-19).
• Mormons believe that matter is eternal but God is not. Christians believe that God is eternal (Gen. 21:33; Deut. 33:27; Jer. 10:10).
• Mormons teach that Lucifer is the younger brother of Jesus. Christians believe that Satan is a created being (Ezek. 28:12, 14-17).
• Mormons believe that everyone who has ever lived existed first as an “intelligence” who lived in eternal matter. The bible teaches that every person had his or her beginning on earth at the time of conception (Ps. 139:13-6).
• The Mormon concept of salvation comes in two parts: general and individual. They believe that all humanity will be saved when they are resurrected and will be judged on their works. If a person wants to earn forgiveness from personal sins, he must meet certain requirements, including faith in Christ, baptism by immersion, obedience to the teachings of the Mormon Church, good works, and the keeping of the commandments of God. Christians believe that salvation is a free gift of God though faith not works (Rom. 6:23; 10-9; Eph. 2:8-9).
• Mormons believe that everyone must learn to become a god, the same as all gods have done, by moving from one small degree to another. The Bible is clear that there is only one God—none before and one after. He is changeless (Isa. 43:10; Hos. 11:9; Mal. 3:6).
• Mormons believe that the Trinity is three gods—with distinct bodies, except for the Holy Spirit, who has never been able to become a man and has only a spirit body. Christians believe that the Trinity is one God whose essence is found in three persons (John 1:3; Col. 1:16; 2 Cor. 5:19; Eph. 2:18; Gen. 1:26; Ps. 110:1; Isa. 7:14, 48:16; 61:1; 1 Cor. 8:6; Heb. 1:8-10; Acts 5:3-4; Deut. 6:4).
• Mormons accept as the “word of God” the Book of Mormon, doctrine and Covenants and Pearl of Great Price; they do not, however, accept the whole bible because of errors in translation. They also believe that God continues to speak new revelations because they are necessary. Christians believe that there is no new revelation from God and that the Bible is complete and without error (2 Tim. 3:16; Jude 3: Gal. 1:8; 2 Pet. 1:3).
• Mormons teach that most of humanity will end up in one of three levels of heaven: telestial, terrestrial, or celestial. Eternal life in celestial heaven is only for Mormons. Christians believe that heaven is God’s dwelling place (Ps. 73:25) and will be the home for all those who believe in the complete payment for personal sins accomplished by Jesus on the cross (1 John 4:10j). Ultimately, heaven is to be in the presence of Christ (Luke 23:43; John 14:3; 2 cor. 5:8; 12 John 3:2).
David777, an apologist once came to our church about 10 years ago and spoke on Mormonism. A point which he made that still sticks with me is and I quote "When you talk to Mormons, remember one thing. They use a different dictionary than you do." What he meant was that we use the same words, but the meanings are different.
I've interacted with them, and tried to witness to them (work for one) and though they honestly see themselves as Christians, they react probably as most do when confronted with the differences. They either move on, or attack. So, always in dealing with them try to show the Love of Christ in all your conversations with them!
Pray and always use scripture when possible, when you talk to them.
I pray that the little I've typed here will help you.
YBIC