A ghost question -- Part research and part for a friend --

Does anyone know how to stop random ghosts from attaching to people and following them home?

I have friends who are dealing with this -- one parent and a small child see ghosts, and the father has had to firmly run off a couple of spirits who were probably picked up off the greenbelt or something.

You may think they're nuts, so this is for the people who don't think it's a crazy question at all. Feel free to respond by LJ email.