Entrance
It's not a popular idea, but it is the truth: "Evil enters through sin." Unfortunately, this can be personal sin, household sin, generational or racial sin. Adam and Eve was separated from direct fellowship with God because of sin, and we continue in the struggle with sin and its consequences.
Sin comes in many forms. There are diverse definitions of sin, and that is beyond the scope of this writing. However, my personal definition of sin is that which separates us from a relationship with our heavenly Father.
It may come from evil acts, lustful thinking or even playful participation with darkness. Pain, fear and pride can cause sin and can create an entrance for the demonic. Such kinds of events establish tormenting attitudes in our lives which can have a great affect upon us.
People who have suffered great pain are most apt to inflict pain upon others. When subjected to painful humiliation or abuse, a victim personality may develop. The victim replays the events whereby an alternate-personality forms as a revenger or protector who strikes back, sometime years later at others who had nothing to do with the original pain. The negative energy generated from this act of revenge feeds the tormentors, and they become insatiable. Suddenly, evil directs this person's activities in increasingly dreadful ways.
Tracking
Understanding the tracking nature of demons is a great help in overcoming them. Demons find us the same way wolves find prey in the forest - they smell the flesh of their prey. The short answer is to walk in the Spirit (Galations 5) and not by flesh, and you won't smell like prey. This is how you may walk among demons without them attacking you.
Overcoming
Walking in the Spirit is a wonderful answer to both the demonic entrance and tracking of evil in all its manifestations. However, comes the question to mind: "How do I do that?" The answer to this question is in the Biblical truth that "goodness over comes evil."
Another question: How does the natural mind bring forth the goodness of God? It cannot in a natural way, for a goodness is Fruit of the Spirit or a Kingdom thing. Ultimately, our inquiry should be how to operate in the fullness of the Kingdom on earth as it is in heaven.
Fullness of the Kingdom
For two thousand years there has been a great short coming of the traditional churches, particularly in the USA, failing to even define the fullness of the Kingdom.
Jesus was sent to redeem us from sin, so as to restore us into fellowship. The Holy Spirit continues with us for the provision of truth and power. Yet, this is incomplete without a personal relationship with the Father, giving us direction in the Kingdom on earth.
A strong personal relationship with the creator of the universe is not only possible, but it is invited . This was the secret to Jesus' miraculous work on earth, and He promised to take us to the Father. Thus, there is validity to the Scripture, "...greater things you will do (John 14:12)."