Do I believe in miracles and other supernatural happenings? You bet I do! I have been the beneficiary of some of them myself, and have witnessed these things on several occasions.
So. How can one tell the difference? For one thing, when a healing or other manifestation of God’s power occurs, the focus is ALWAYS on Jesus. Sometimes he uses his servants to impart the blessing, but those servants never take the credit. And you can bet they won’t be covered in tattoos and body piercings, yelling and screaming, whipping people into a frenzy, and focusing on the power they have.
The times I have experienced the supernatural power of God, it was always unexpected. I never had to conjure up faith, or profess that I had the thing that I wanted. There were no frenzies, no formulas, I did NOTHING to get God to act. The Lord sovereignly and unexpectedly blessed me, and then left. And each experience has stood the test of time. Over the past thirty years since being "born again," I have never again been bothered by anything that the Lord has healed in me, or set me free of.