Depends on what your teacher or whatever wants to hear. Most people will say Polygamy. But some of his basic beliefs are actually what Latter-Day Saint members live by, the Articles of Faith. Basically he believes in the god head, consisting of Heavenly Father, Jesus Christ, and the Holy Ghost, he believes that all other religions are not 100% the true church but contains some fragments of the true church from when it fell. Etc.
Source: I am LDS.
