Understand your authority.

“She started following Paul around, calling everyone's attention to us by yelling out, "These men are working for the Most High God. They're laying out the road of salvation for you!"”          
Acts 16:17(MSG) 

Our opening scripture tells us about a girl who was following Paul everywhere shouting out to everyone that they were working for the Most High God, showing the way of salvation.

Now I want you to understand that the fact that someone is speaking in the Lord's Name does not mean that they are from the Lord. The Bible reveals this to us clearly in Acts 16:16 that the girl who was shouting and telling every one that the Apostle Paul and those with him were working for the Most High God was actually possessed with the spirit of divination.

Divination when translated from the greek means python. This evil spirit was what enabled her to know these things and made her a fortune teller. So, when she saw Paul and those with him, she knew by that evil spirit who they were and what they were sent to do, and she voiced it to everyone everyday as she followed them until the Bible says in Acts 16:18, “…But Paul, being grieved, turned and said to the spirit, I command thee in the name of Jesus Christ to come out of her. And he came out the same hour.”

Paul was able to cast out that evil spirit from that girl because he understood the authority he had in the Name of Jesus to command and enforce obedience and the devil came out the same hour.

Confession.
All devils are my subject in the Name of Jesus. Therefore I bind all the works of every unclean spirit  and I render their works ineffective and unlawful in my immediate sphere of contact in Jesus Name.

For further study read:
 Matthew 17:15-18, Mark 1:25-27, Mark 9:25-27,
Acts 9:32-34, Acts 19:12-17.

Doing the Word.
Whenever you sense the operation of any unclean spirit, do not hesitate to cast it out.