The Main Way To Defeat The Devil
"There is one thing in the world that the devil is afraid of; and that is the shed blood of Jesus Christ. When you know what a person is afraid of, you know how to defeat him. Many Christians, who have been sorely tempted, have surrendered themselves to God afresh, and have called for the protection of the blood of Christ. Satan left them, and they were calm and peaceful."

From the bible tract, Two Ways To Defeat The Devil, by Mrs. Dewitt Smith, for Pilgrim Tract Society, Inc., Randleman, NC.

Of course, the MAIN way to defeat the devil is to first admit that he exists. He originally had the position of an angel with high authority. His name was Lucifer, and he was a very beautiful creature in God's creation. He fell from that position, and many angels chose to fall with him. He is now called Satan. You can't believe in a guardian angel for yourself or your children, or in cherubims and seraphims who praise God day in and day out, without admitting that Satan exists. He was one of them, and if they exist, then he exists.