The doctrine that most shapes Latter-day Saint life is not any particular teaching but continuing revelation, and its governance consequences are unusual.
At the head stands the President of the Church, held to be a prophet, seer and revelator, with two counsellors forming the First Presidency, and beneath them the Quorum of the Twelve Apostles. Succession is not by election in any contested sense: the longest-serving apostle becomes president, which makes the office predictable and almost always elderly. Decisions of the First Presidency and the Twelve are made by unanimity. Below that, local congregations are wards led by a bishop who is an unpaid layman with a full-time job elsewhere; there is no professional clergy, and the entire operating structure of a ward is staffed by members on temporary assignment.
Because revelation is held to be open, official teaching can change, and it has, twice in ways that reshaped the church. Plural marriage was taught as a divine principle, defended through decades of federal prosecution, and withdrawn by the 1890 Manifesto after the church's property was seized and statehood for Utah was blocked; a further statement in 1904 ended the practice fully, and the church now excommunicates for it, while fundamentalist groups that continued it split away. And the restriction barring men of Black African descent from the priesthood and both men and women from temple ordinances stood from the mid-nineteenth century until it was lifted by revelation in 1978. The church published an essay in 2013 disavowing the theories that had been advanced to justify it.
Both episodes are usually raised by critics as evidence of expedience and by members as evidence that the channel is open. The church does not dispute the facts of either.