There are only 2 ways in which a man can be possessed and oppressed by a demon. The first way which accounts for 90% of demonic possession is when mankind willfully allows the possession. His permission is necessary because man is made in the image of God and has a sovereign will like God, and no one can violate that without his permission. The second method is when man lowers himself and his sovereign will by practicing wicked things.
1. Infestation
The demon is seeking approval at this stage, approval to stay. It almost needs permission to begin to reveal it's true self. He comes in a friendly way, slowly increases in tempo as the he gains strength the chosen individual looses his or hers strength. Everyone addicted of drugs first did it once, and again, and again, until it took over his system.
2. Oppression
At this stage he moves into full attack mode. This can be physical, mental, and psychical in nature and is designed to break the affected person's will to live. Depression is often a symptom at this stage, and as the will and faith of the individual is reaching breaking point, the demonic entity will move onto the third and final stage, called Possession.
3. Possession
The Demon now has sufficient power and hold over the individual, typically the person affected will have little to no self worth, will or faith left. The evil entity will be in control more often than not, and the influenced may well be hearing voices telling them to do harm to others or themselves. Manipulation is at an all time high, and the very soul of the individual it at stake.The demon's goal at this point is to drive the affected to suicide, and to take as many people with them on the way, thus condemning their soul to eternity in hell.