my technique for this is to see how it goes. if they become troublesome then I would ask firmly for them to leave once casting a protection circle.
If he is not doing any harm then put on a tape recorder and ask series of questions, leave a minute or two gap each time. now try to turn the recorder up and see if you get any answers, though I cannot stress this enough DONT DO IT ALONE.
Never confront a spirit alone unless you confident, ghosts can be worse especially if you upset them. always have a friend handy. I keep thinking about joining a ghost hunters society, but I want to join a decent one not a pack of charlatans.