The article below has excellent advice for families who may believe their home is haunted.
How To Remove A Ghost
The only thing I would add is that the salt should be put in the corners of the room(s). Seances and Ouija boards do not "feed" negative spirits, but rather could be used by negative spirits to invoke fear in people. Negative spirits prey on fear. So the rule of thumb is don't feed the bad ghosties. Be firm and tell negative spirits to leave.