The first voice
The book of Revelation is prophetic and full of symbolism. Therefore people have many theories on its meaning and interpretation. It is important to follow sound principles of Bible study at all times, but especially with such parts which can be manipulated to fit people's ideas. Principles such as scripture interpreting scripture, not reading into a passage what is not actually there, keeping scripture in the context of the passage and the Bible as a whole, not turning the Bible into an occultic secret code book, not making doctrine out of symbolic passages, not ignoring other passages that contradict your theory, to some degree the first mention proinciple, and avoiding the cool or trendy interpretation looking for the "wow" factor from people must be followed to gain the correct understanding of scripture. Also, we must be humble enough to admit we don't know everything. Even great prophets such as Ezekiel, Daniel, and even John the writer of Revelation had to do this.
Revelation 4:1 says, "After this I looked, and, behold, a door was opened in heaven: and the first voice which I heard was as it were of a trumpet talking with me; which said, Come up hither, and I will shew thee things which must be hereafter." Some people believe this is a symbolic representation of the event Christians call the rapture, which is described in such passages as 1Corinthians 15 and 1Thessalonians 4. One thing of note here is that John was listening the the first voice that spoke to him. He was referring to the voice he heard in chapter 1 of Revelation, which was the voice of the Lord Jesus Christ. This is an essential lesson for anyone desiring a relationship with the Lord.
In Deuteronomy 2, Moses gave his last sermon to the next generation of Israelites who were about the enter the promised land led by Joshua. Moses himself was not allowed to cross over Jordan with them. He was about to die, so he was giving the people one last admonition to keep the commandments God gave them on Mount Sinai. He reminded them that when God was speaking at the mountain, He did not show Himself to them in a visible form, but they audibly heard His voice. He was warning them against idolatry. He was reminding them that they were about to enter a land filled with idols and other religious beliefs and practices. They were to remember the "first voice" and not listen to any other.
In John chapter 10, Jesus said that He is the shepherd, and his followers are His sheep. Just as sheep learn the voice of the shepherd, we are to know His voice and be able to distinguish it from all others. We are to only follow His voice. He warns of imposters that will attempt to imitate Him. It is our responsibility to know His voice and follow it only. This may seem like a difficult task, especially in the technological age we live in with easy access to so many voices. How do we know the "first voice"? The first and most important way is to know the Bible enough to be able to tell the truth from a false interpretation. There is no clearer or direct voice of God than His written word - the Bible. Another way is to be filled with the Holy Ghost, which is the Spirit of truth. The Spirit of the author will live inside us and guide us into all truth (Jn 16:13). Another way is to have a consistent devotion to prayer. Regular communication with God is a sure way to get to know Him and His voice. Prayer is more than just us listing our requests to God. It is two way communication, and God will never speak something to us in prayer that contradicts what He has already spoken in the Bible. We can also hear the voice of God through Biblical preaching. Not all preaching is Biblical. Jesus and the apostles repeatedly said this. We can hear the voice of God through Biblical leaders, and other people. We need to make sure we are only following the "first voice".