Know Your Weapons
The Christian's weapons are the name of Jesus Christ, the blood of Jesus Christ, and the Word of God. We also need the Holy Spirit's discernment, and sometimes he even supplies the words to say. You must be clear about this, that we cast out spirits by our words - we don't fight witchcraft with witchcraft. Avoid superstitious ideas for confronting demons such as 'holy water' etc. Matt 8:16
When evening came, many who were demonised were brought to him, and he drove out the spirits with a word and healed all the sick; 2 Thess 2:8
And then the lawless one will be revealed, whom the Lord Jesus will overthrow with the breath of his mouth and destroy by the splendour of his coming; Rev 1:16
In his right hand he held seven stars, and out of his mouth came a double-edged sword; Rev 12:11
They overcome him by the blood of the lamb and by the word of their testimony
At first great difficulty may be experienced in speaking out loud to demons, especially when they do not respond - this is pressure from the enemy. It is very effective to quote scripture - Jesus did when tempted by the devil, Matt 4:1-11
Then Jesus was led by the Spirit into the desert to be tempted by the devil.
After fasting for forty days and forty nights, he was hungry.
The tempter came to him and said, "If you are the Son of God, tell these stones to become bread".
Jesus answered, "It is written: 'Man does not live on bread alone but on every word that comes from the mouth of God"'
Then the devil took him to the holy city and had him stand on the highest point of the temple.
"If you are the Son of God," he said, "throw yourself down.
For it is written: 'He will command his angels concerning you. and they will lift you up in their hands, so that you will not strike your foot against a stoner"
Jesus answered him, "It is also written: 'Do not put the Lord your God to the test."'Again, the devil took him to a very high mountain and showed him all the kingdoms of the world and their splendour.
"All this I will give you, "he said, "if you will bow down and worship me." Jesus said to him, "Away from me, Satan! For it is written: 'Worship the Lord your God, and serve him only."' Then the devil left him, and angels came and attended him.It is also good to magnify and praise Jesus and even to sing (be open to the Holy Spirit's lead).
Tell the spirits what Jesus has done and what their end is. Quote scriptures that are against the particular activity of the spirit you are dealing with. For example, if you are up against a spirit of hatred, you might say, "This person loves Jesus, for the love of God has been shed abroad in his heart" (Rom 5:5).