It's All in the Preparation...
The best way to prepare for a sitting is to come with an open mind. Mediumship work deals with tuning in to a field of energy that then impacts the body’s sensory systems, so if you are coming in with expectations, you narrow your energy field and actually make it more difficult to receive a good, accurate amount of information. This does not mean you cannot be skeptical or toss aside your powers of discernment — only you can determine the validity of the information coming through!
Also, come with knowledge regarding the background and history of your family. Armed with this knowledge, you will be able to validate the information more quickly, and allow for a smoother session. Jeffrey cannot guarantee he will make contact with any particular person, so again, come with an open mind and without expectations (but retain discernment). This will allow your energy field to be more open, and hopefully whoever you might be wishing to contact will be able to come through easily. A few days before the session, it is a good idea to send your thoughts toward those who you would like to hear from, so they can get ready.
Jeffrey does record his private sittings and offers free download from the internet afterwards.
Above all, Be relaxed. Be comfortable. And enjoy the sitting.