The devil is real, and he is certainly powerful; how else can you explain all the hatred and evil and death in the world? But no -- he is not equal to God, nor is he as strong as God. When the devil tried to get Job to turn against God, he first had to get God's permission to do so (see Job 1:12).
How does the devil operate? Sometimes he operates very openly, causing people to attack God and His servants, and even making them worship him instead of God. Whenever I hear of people who've been tortured or put to death for their faith in Christ, I know Satan has been at work. Even in our supposedly sophisticated society today, some people deliberately turn from God and serve the one the Bible calls "the prince of demons" (Mark 3:22).
But the devil often works in more subtle or hidden ways. When we think we can sin and get by with it, we're falling for the devil's lies. When we allow greed or jealousy or anger to overcome us, we're giving in to the devil's influence. When we think we don't need God and believe we can run our lives without Him, we've let our minds be blinded by his deceptions. The Bible says that Satan works "in every sort of evil that deceives those who are perishing" (2 Thessalonians 2:10).
Don't become preoccupied with the devil, however -- for he is a defeated foe! By His death and resurrection Jesus Christ defeated sin and death and hell and Satan. Have you put your life into His hands?