On your first visit there's an in depth discussion with your practitioner about what brought you in for treatment, your past experiences with your health, as well as the current state of your health generally. Once the discussion is completed, the actual process of your treatment will be explained and any questions you have will be answered. Since every treatment is tailored to your individual constitution and condition it would be difficult to describe the specifics of your treatment.
Generally though, you should expect a very relaxing and comfortable experience. It is best to wear loose fitting clothing that could be adjusted to allow access to the extremities. Please try your best to refrain from ingesting stimulants or depressants (coffee, alcohol, narcotics, tobacco, etc.) for 24 hours prior to and following your scheduled treatment time.