Being able to recognize how God speak is a crucial thing for every human to know. There are a number of ways in which God speaks.
The most important and only infallible way that God speaks to people is through the Holy bible. Even though the writers of the Bible were not infallible, the inspired words and teaching of the Bible, the Holy Scriptures, are.
The Bible to the Christian is the Word of God. It is God communicating His thoughts to you through the printed page. If you wish to know what God thinks about anything, seek the answer in the words of the Holy Scriptures.
The Bible is God’s revelation of Himself through the writings of the Prophets, Apostles and other writers of the Old and New Testaments.
Jesus and the Apostles never relied on the teachings of theologians or philosophers or the religious experiences of other persons as the authority and basis of their teachings.
It is clear in the New Testament that Jesus and the Apostles constantly quoted the Old Testament Scriptures as their source of authority and teaching.
In the Gospels and the Book of Acts and see how many times Jesus and the Apostles quote the Old Testament Scriptures. The Apostles also regarded every word of Jesus as later recorded in the New Testament as being the Word of God.