Discerning well isn't about being suspicious of everything, but about gently learning to recognize God's fingerprints in the fruit, patience, kindness, self-control, joy. Over time, the truth reveals itself in what remains and what leads to life.
Are there people, ideas, or habits in your life that seem good on the surface--but when you look closer, do not lead to peace or holiness? What kind of fruit are you bearing in your own life right now?