I have heard that the key to detecting counterfeit money is to be intimately familiar with the real thing. This is also true when it comes to spiritual talk. The key to detecting false teaching is to be intimately familiar with the truth - that is, the revealed Word of God in the Scriptures, the testimony of the prophets and apostles, especially what they have to say about the person and work of Christ.
As you encounter various spiritual ideas, see if they pass the test. Compare them to what you have learned from and see in the Bible. And prepare for that task by becoming more and more familiar with God’s Word. “That is how we can distinguish between the spirit of truth and the spirit of error” (1 John 4:6).