1 John 4:2
 By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, (ESV)
When you hear someone teach what they claim is truth do you consider that there is a spirit behind that voice directing the conversation? John is telling us exactly that. So, when you listen to a teacher you need to listen to the spirit. Does the person speaking acknowledge that Jesus Christ is exactly who he said he was? If so, you are listening to the Holy Spirit. If not, there is a demonic spirit speaking.
John's test for determining whether God's Holy Spirit is speaking is a doctrinal test. The specific doctrine here is the incarnation. The incarnation is God becoming flesh. Jesus is God eternal who took on human flesh. He was both God and Man on earth. If you look at all kinds of various cults that have come about you will find one unifying theme; they deny the incarnation in one way or another. Listen to how the Apostle Paul describes Jesus:
 He is the image of the invisible God, the firstborn of all creation.  For by him all things were created, in heaven and on earth, visible and invisible, whether thrones or dominions or rulers or authorities—all things were created through him and for him.  And he is before all things, and in him all things hold together.  And he is the head of the body, the church. He is the beginning, the firstborn from the dead, that in everything he might be preeminent. (ESV)
Notice that Paul talks of his being in the flesh by describing him as the "image of the invisible God." He is God made flesh. However, he also speaks of him as the Creator. Do you consider Jesus as Creator? He is before all things. That speaks of his eternal nature. And he is above all things. He is all powerful. He is fully God.
When you are unsure if a teacher is speaking truth concerning Christ, check the Word of God! This passage in Colossians is a great place to go to be reminded about exactly who Jesus is. If the teacher's words do not pass the doctrinal test of the Incarnation you need to be concerned that it is not the Holy Spirit inspiring their words.
When you hear someone talk about God, do not just blindly believe everything that they say. Test the spirit behind their words by checking the truth with what the Bible says.