"Beware of false prophets, which come to you in sheep's clothing, but inwardly they are ravening wolves," (Matthew 7:15).
You will never meet anyone who will say, "I am a false prophet, follow me." He will present himself as a true prophet, and he will appear to be true. But, you must search deeper and examine his "fruit," that is, his prophecies and teachings. The best method of discerning the truth is by a critical examination, because the truth will stand the strongest test, but error will be exposed.
This thought was expressed by Joseph Fielding Smith in Doctrines of Salvation, Vol. 1, page 188. He said, "Mormonism, as it is called, must stand or fall on the story of Joseph Smith. He was either a prophet of God, divinely called, properly appointed and commissioned, or he was one of the biggest frauds this world has ever seen. There is no middle ground.
"If Joseph Smith was a deceiver, who willfully attempted to mislead the people, then he should be refuted, and his doctrines shown to be false, for the doctrines of an impostor cannot be made to harmonize in all particulars with divine truth. If his claims and declarations were built upon fraud and deceit, there would appear many errors and contradictions, which would be easy to detect. The doctrines of false teachers will not stand the test when tried buy the accepted standards of measurement, the scriptures."
Here’s one prophecy (of many): Doctrine and Covenants 97:19: The prophecy says that "Zion cannot fall, neither be moved out of her place...." But, Zion was moved from JacksonCounty, Missouri. D&C 101:17-21 says "...there is none other place appointed than that which I have appointed;..." Salt Lake City cannot be Zion.