There can be countless reasons for the interaction of a "Jinn" and a normal human being, but the interaction can both be positive and/or negative. In all of the countless reasons of interaction present, there are always three possibilities: The body of the human might be possessed by the Jin i-e it may be inside it, outside it or going in and out according to its own will. During the time interval that he is in control the body, he may speak through the person and/or possess him: this can be permanent, periodic or occasional or at times all thrice in small intervals leaving the human impaired.
Sorcery:Sorcery is one of the most frequent reasons for a "Jinn" to possess a human body. This doesn't necessarily mean that it has to be an adjunct by a "Jinn", but Jinns are; at some time of the process sent or strengthen the affect on the human. Examples can be: to make a couple breaks up with each other and/or possible divorce if the couple is married. What a jinn is capable of, is that it can denote the man a sickening or alarming appearance in the eyes of his wife; to prevent someone working they will get the employer to reject him or not trust him. But the most that jinns do is to mentally disturb the victim.
Revenge& Love:The jinns too live on the same world and inhabit the same environment as the "Seen" creatures or the normal and ordinary human beings. The most probable places where a jinn might live are public bathrooms, Trash disposal dumps and cemeteries. For the reason, that a Jinn can watch us while we can't, the Prophet Muhammad (peace and blessings be upon him) trained us many ways to guard ourselves against the harm they might bring to us.
Reciting Bismillah (in the Name of Allah) before walking into someone's house, having a meal or drinking water, and having intercourse will keep Shaitan/Iblees/Satan/Lucifer from entering the house and/or partaking with a person in his food, drink and sexual activity.