Just say " Boo & go away " Works every time :)
For 19.99 u can have the Otis Campbell ghost killer it slices dices chopes purees a ghost
Call Bill Murray ... GHOSTBUSTERS !
The thing is they are already dead. That is how they got to be a ghost.
If you want it to leave you alone, according to the shows with psychics on them, just tell them in a stern voice to leave you alone. Or tell them that you realize they used to live there, but now it is your home and they need to stop bothering you.