If you've decided to hire the services of a medium, for whatever reasons, there are a few things you should keep in mind to guarantee you get the best session possible. First of all, try to come in with an open mind. You may be feeling skeptical, but if you let that be an issue, it can certainly color your results. A corollary to that is that it's important, to be honest about why you're there. If you're only trying to debunk things or to expose the medium as a fraud, go ahead and admit it up front. A medium who's legitimate will probably still be willing to work with you.
Spiritualists believe that phenomena produced by mediums (both mental and physical mediumship) are the result of external spirit agencies. The psychical researcher Thomson Jay Hudson in The Law of Psychic Phenomena (1892) and Théodore Flournoy in his book Spiritism and Psychology (1911) wrote that all kinds of mediumship could be explained by suggestion and telepathy from the medium and that there was no evidence for the spirit hypothesis. The idea of mediumship being explained by telepathy was later merged into the "super-ESP" hypothesis of mediumship which is currently advocated by some parapsychologists.
Do compose your emotions and appearance to hide any revealing information about yourself. Your facial expression, style of dress, personal mannerisms, and emotional outbursts can tell a psychic, especially a false one, a great deal about you to make it look like she knows all these things from a paranormal reading, when in fact, she is merely interpreting your physical appearance or reactions.