It is important to acknowledge that it is very rare for a person to become possessed, even more to immediately become possessed by a demonic spirit out of the blue. There are typically three stages of possession. 

Infestation: In various ways, the spirit or spirits will demonstrate that they are there, and they will often do things to bring your attention to their presence. That's the whispering, the footsteps, the feeling of another presence, it can manifest in poltergeist activities, which ultimately grows into oppression.

Oppression: This is the stage where the victim, and it's usually the one who's the most psychologically vulnerable, is targeted specifically by an external force. Breaks the victim down, crushes their will. The struggle is not between the spirit and the person, but is between the person’s willingness to give him or her self over to the possession fighting against their reluctance to release control of themselves to something else.  And once in a weakened state, leads into the third stage, possession. 

Possession: At this stage, the spirit fully possesses the individual.  Any struggle and adjustment ceases, and the spirit can speak, act, and live through the body of the individual.  This is where possession has its real benefit.  As the person who is possessed, you basically become a passenger in your own body and mind.  

Poster Credit: C L U B ╳ R E B I R T H