Ghosts don't generally haunt people - they generally haunt a place. People just simply are around that place. There have been, on rare occasions, people that have been haunted - regardless of where they live or move to, the ghost stays with them. But for the most part a ghost will remain in a place because in life that is what they knew and in death they still believe they are supposed to be there. 

Ghosts generally hang on to the physical world because of unfinished business or because their death was surprise. Most people are aware on some level that death is coming - so it rarely a surprise when it happens...but some people never get the message and when death does happen it is a shock and they don't accept it....hence the result is haunting. 

There are times when a ghost will attach itself to a person - for example - one of our Team Eeeek Members had this experience. We went to a haunted location for a primarily study of the haunted house and the ghost came home with one of our members. She began experiencing some very strange things in her house - things that never happened prior to this - like lights being turned on and off - curtains moving when there was no wind or window/door open to cause this. But when we returned to the haunted location we simply told the ghost it could not remain with our Team member and if it did not wish to cross over to the spiritual side where it belonged it would have to remain with the house it had been haunting. It did - as far as we know stay with the house and not with our team member.