It is big business in some part of the UK so attend meetings where someone starts talking to deceased people. The techniques involved in pretending to do this are well documented not the least by Erik Weisz (Harry Houdini) who spent years trying to talk to his mother and called all such Mediums charlatans.
But there is a very real way we can communicate with those who have died and that is through their work. When I first read Balzac I knew that these were not just stories but this was the way people were and even are. Novels are instruction sets to human character and human ideas. And not just novels. Anything people have made, tells us about them and about us. When you look at a Mayan statue never forget it is telling you something about your humanity as well as telling you something about how certain humans lived. So often we think we are disconnected from the things we find because our immediate ancestors took a slightly different intellectual path, but nothing made is separate from us.
And even those things which are the hardest to know and exist only in the imagination, those people who did not make anything for us to find or write anything down for us to read, even they tell us something. For even in the decision not to create art we are informed as to our natures.