For one, avoid participating in anything to do with the evil side of the spirit world (see Ephesians 5:11). Instead of harboring dark thoughts that can lead to being influenced by dark forces, the Bible clearly tells us to focus on the positive: "Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy—meditate on these things" (Philippians 4:8).
Respect the power of the dark world and don't play around with it. Avoid any type of séances, gothic rituals or such devices as Ouija boards, all of which can open portals to the evil world. At the same time, don't be afraid of the dark forces. Remember, God is still in charge and is far more powerful than any of these evil agents. The Bible tells us, "He who is in you is greater than he who is in the world" (1 John 4:4).
Make sure to draw close to God. By doing so, you'll move farther away from the world's evil sources. Through prayer, Bible study, meditation and occasional fasting, you will be greatly strengthened and will successfully resist Satan's temptations. "Therefore submit to God. Resist the devil and he will flee from you. Draw near to God and He will draw near to you" (James 4:7-8).
If you ever feel there is a strange and evil presence around you, the Bible gives advice based on the confrontation between the archangel Michael and Satan. "Yet Michael the archangel, in contending with the devil, when he disputed about the body of Moses, dared not bring against him a reviling accusation, but said, 'The Lord rebuke you!'" (Jude 1:9).
So, if you do rebuke a spirit, don't do it in your name, but always in God's name, providing you have a relationship with God through Jesus Christ. That is the only authority evil spirits respect. Realize also that the spirit world is nothing to be trifled with (Acts 19:13-17). If you feel troubled by a spirit, you should seek counsel and advice from one of God's true ministers.
Another great source of spiritual strength is simply reading and studying the Bible. Jesus Christ quoted Scripture numerous times to successfully counter the wiles of the devil (Matthew 4:3-10). Many scriptural passages—especially in the book of Psalms —provide comfort and courage when one is facing dark spiritual forces. Take particular note of Psalms 23, 27, 34, 37 and 91.