The question is sometimes put forward of what the church actually believes. And what do I believe myself? Do all LDS believe the same thing? And if not, then why not? And if so why do some general authorities seem to have opposing opinions here and there over the years?
If all members (regardless of their areas of responsibility in the church - callings) believed the same thing then something would be very wrong.
"For look, this is what the Lord God says: I will give to the children of men line upon line, precept upon precept, here a little and there a little; and blessed are those who take note of my precepts, and lend an ear to my counsel, for they shall learn wisdom; for to him that receives I will give more; and from them that shall say, We have enough, from them shall be taken away even that which they have." 2 Nephi 28:30
Here Nephi has expressed that the Lord gives a person knowledge a piece at a time, as they are ready. And those who don't accept it not only won't get any more, but will actually start to lose that which they have. In regard this idea Alma expresses that God won't even make it available to those who don't accept and enthusiastically obey what he has already given.
"And now Alma began to expound these things to him saying: It is given to many to know the mysteries of God; nevertheless they are laid under a strict command that they shall not impart only according to the portion of his word which he grants to the children of men, according to the heed and diligence which they give to him. And therefore, he that will harden his heart, the same receives the lesser portion of the word; and he that will not harden his heart, to him is given the greater portion of the word, until it is given to him to know the mysteries of God until he knows them in full. And they that will harden their hearts, to them is given the lesser portion of the word until they know nothing concerning his mysteries..." Alma 12:9-11
This statement of Alma's points out the huge gap that will exist between those accepting previously hidden knowledge and those who don't. It also points out that the diligence with which they accept and obey the knowledge counts. Additionally it is presenting that people will grow in this knowledge until they know the mysteries in full. This latter is saying that the person does this by a growth process that obviously takes time. Thus people will be on different levels of doctrinal understanding on each of the many subjects we need to learn.
These new doctrines must be learnt independently. They aren't taught by presidents of the church. The president of the church very rarely presents new doctrine. The last time was in 1978. Thus the rate of learning new doctrine is the responsibility of the individual.
The then president of the church, Joseph Smith, taught this same principle.
"Joseph Smith taught that every man and woman should seek the Lord for wisdom, that they might get knowledge from Him who is the fountain of knowledge.." George A. Smith (Deseret News: Semiweekly; Nov 29 1870)
"The things of God are of deep import; and time, and experience, and careful and ponderous and solemn thoughts can only find them out. Thy mind, O man: if thou wilt lead a soul unto salvation, must stretch as high as the utmost heavens, and search into and contemplate the darkest abyss, and the broad expanse of eternity- thou must commune with God." Joseph Smith (History of the Church 3:295-296, Mar 20 1839)
Many such truths exist in the Scriptures and in comments expressed by some past members with all sorts of callings (including those assigned as church president). As the Spirit works in us to enlighten our understanding we can reject this or accept it. Thus we have a great difference in opinion of individuals regardless of their positions.
We also see differences of levels of doctrinal understanding existing within the church just after Christ died.
"I have fed you with milk, and not with meat: for before now you were not able to bear it, and even now you are not able." 1 Cor 3:2
So Paul is declaring he had knowledge which he wasn't giving to the Corinthians. In regard this knowledge he said that they should be receiving it, but were too slack.
"For by this time you ought to be teachers, yet you have need that one teaches you again that which is the first principles of the oracles of God; and have become one of those that has need of milk, and not of strong meat. For every one that uses milk is unskilful in the word of righteousness: for he is a babe. But strong meat belongs to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil." Heb 5:12-14
When Christ was doing his mission there was also a difference of ability to understand his sayings in the Jewish church of God (originally established through Moses).
"There was a division among the Jews for these sayings." John 10:19
At the time of Moses there was a similar circumstance. In regard Israel at Moses' time Paul stated,
"For we also have had the gospel preached to us, just as they did; but the message they heard was of no value to them, because those who heard did not combine it with faith." Heb 4:2
So a variety of understanding is going to exist among members at any time of history. Today is no different.
Yet in regard what could be classified as church doctrine this would depend on what church member you asked. I believe we have to make a line between church doctrine and doctrine believed by church members. To me the church doctrine should be the basics presented in the Standard Works of Scripture. That is that we believe in Jesus Christ as the special Son of Heavenly Father. We believe that Heavenly Father and Jesus Christ are resurrected human beings and that we are entirely in their image AND likeness. We believe that he atoned for the sins of those who truly repent. And he makes possible the resurrection. We believe that the Church of Jesus Christ of Latter-Day Saints is the kingdom of God on earth. We believe that God has given authority to certain men within the church to perform the sacred ordinances as he would have them done. We believe in revelation from God to mankind. We believe in using the gift of the Holy Ghost. We believe in prayer. We believe in learning and doing those things that God would have us do. We believe in the restoration of authority by Jesus Christ to Joseph Smith.
In fact we could turn to the 13 Articles of Faith, and use those as a statement of what church doctrine is.
There are members that want to add seemingly endless amounts of manuals, magazines, books of their choice and other materials to the above list. Promoters of this seem to only believe these materials where they agree with them. If they don't they will usually say that it isn't what the current prophet is saying (Where the quote isn't from him - which is most of the time), and suddenly that makes that source incorrect for that quote. Sadly they will even try this sometimes with the Standard Works.
In regard these materials and "the current prophet" philosophies I'd like to give two quotes, from such materials and the current prophet at the time; Harold B. Lee:
"Stand Ye in Holy Places" by Harold B. Lee 15:162:6
"It is not to be thought that every word spoken by the General Authorities is inspired, or that they are moved upon by the Holy Ghost in everything they write. I don't care what his position is, if he writes something or speaks something that goes beyond anything that you can find in the standard church works, unless that one be the prophet, seer, and revelator--please note that one exception--you may immediately say, "Well, that is his own idea." And if he says something that contradicts what is found in the standard church works, you may know by that same token that it is false, REGARDLESS OF THE POSITION OF THE MAN WHO SAYS IT [my emphasis]." Also quoted in the Seminaries and Institute manual (1974), printed when he was the current prophet.
When church president, Harold B. Lee said in a European area conference:
"If anyone, regardless of his position in the Church, were to advance a doctrine that is not substantiated by the standard Church works, meaning the Bible, the Book of Mormon, the Doctrine and Covenants, and the Pearl of Great Price, you may know that his statement is merely his private opinion. The only one authorized to bring forth any new doctrine is the President of the Church, who, when he does, will declare it as revelation from God, and it will be so accepted by the Council of the Twelve and sustained by the body of the Church. And if any man speak a doctrine which contradicts what is in the standard Church works, you may know by that same token that it is false and you are not bound to accept it as truth." The First Area General Conference for Germany, Austria, Holland, Italy, Switzerland, France, Belgium, and Spain of the Church of Jesus Christ of Latter-day Saints, held in Munich Germany, August 24-26, 1973, with Reports and Discourses, 69.
When new doctrine is sustained by the members then it is placed in the Standard Works. These are the only materials that are accepted church doctrine by the entire membership. We don't sustain opinions of men as Scripture merely by sustaining them in their callings. Else I would be claiming that every word spoken by the Mia Maids teacher is the mind and will of the Lord. Let's get real.
To my LDS doctrine, I use the Spirit, as Alma has suggested. I believe direct revelation is given to anyone who serves God and seeks the truth. As this includes myself, I believe in that which I have been inspired with. I have found all the things Heavenly Father, Jesus Christ and the Holy Ghost say to be true. Whether I'm reading the Scriptures or listening to the opinions of people, I listen to the Holy Ghost to advise in regard to its truth and application.