Angels are those beings who have been on an earth like this, and have passed through the same ordeals that we are now passing through. They have kept their first estate far enough to preserve themselves in the Priesthood. They did not so violate the law of the Priesthood and condemn themselves to the sin against the Holy Ghost as to be finally lost. They are not crowned with the celestial ones. They are persons who have lived upon an earth, but did not magnify the Priesthood in that high degree that many others have done who have become Gods, even the sons of God. Human beings that pertain to this world, who do not magnify or are not capable of magnifying their high calling in the Priesthood and receive crowns of glory, immortality, and eternal lives, will also, when they again receive their bodies, become angels and will receive a glory. They are single, without families or kingdoms to reign over. All the difference between men and angels is, men are passing through the same ordeals that we are now passing through.
[Journal of Discourses 9:102 as quoted at WikiQuotes: Brigham Young, http://en.wikiquote.org/wiki/Brigham_Young]