As a Christian, how do we know what God wants us to believe? That can be hard to determine, especially with different denominations around every corner. There are several things Christians do disagree on, and that’s okay. We are able to disagree about what we call secondary issues. Not because they are less important, but because what the Bible has to say about them is less clear and these issues do not interfere with salvation and holy living. However, the primary beliefs of Christians are those doctrines which are crystal clear in the Bible. We know what God wants us to believe because He gave it to us through his prophets in the Old Testament and the apostles in the New Testament.
The Bible is most clear on these things: men and women were created in the image of God therefore all human life is sacred and ought to be respected and preserved, God designed humanity to be joined in marriage for life as one man and one woman, humanity chose to rebel against its Creator and needed a Savior in order to be reconciled with God, Jesus, God Incarnate, came from heaven to live the life we could not live, die a death we all deserved for our rebellion, came back from the dead three days later as proof of His claims, and the Bible is the inspired Word of God authored by prophets and apostles without error preserved across millennia. Those who commit their lives to Jesus in repentance, love, and obedience are saved from just punishment and will live with Him for eternity. Those who do not are justly punished for their rebellion against heaven. Any person who claims to be a Christian but does not hold these beliefs are outside the lines of orthodox Christianity.
How do we determine what the Bible says is true about any given topic? Read big portions of the Bible, especially whole letters in the New Testament, in order to get literary context. Read up on the cultures of which the authors are writing to. Then ask yourself three questions: what did the author intend to say to the original readers? Which parts of the text are true for all cultures? (Knowing something about the culture of the original audiences helps with this). How do we apply these eternal principals today? These three questions take time and effort to answer because it requires careful study of the text itself and the surrounding cultures. However, it is well worth the effort for the serious Christian.