By using "laying on of hands" technique and specific hand positions, the healer is used as a conduit to channel universal energy onto the receiver with the intent to release blocked energy, clear negativity and toxins, restore balance and raise vibration.

The receiver preferably would be laying on a massage/reiki table, in a quiet, safe, comfortable space.
Although, reiki can be used in an upright position(in a chair, etc)

Reiki works on all levels, mental/emotional, physical, and spiritual. There is no need to be specific, the energy goes where it needs to go, flows where it needs to flow....

Each full session lasts an hour and 15 mins including consultation.

After session, it is advised to continue as long as possible to remain in a stress free environment where as to allow yourself to adjust to the new energy and stabilize. 
This may include going to the gym and participating in an intense workout. This is where it's important to listen to your body mind, spirit and follow what feels right.

Water is important at all times, even more so after a session to assist in flushing out toxins, replenish and for grounding purposes. Of course, eating healthy, light and clean is recommended for at least a few days after session and quite honestly you may crave that more and eating poorly less.

Also be advised that you may experience in days to come, possible discomfort due to releasing of toxic energies.
This may result in anything from cold symptoms to feeling more emotional, to experiencing physical discomfort. Remember it works on all these levels and you will feel the discomfort as well as results depending on where it is needed most.

As far as how many sessions do you need etc, once again, listen to your higher self! You will be guided to the next session.

So relax, and embrace your session. You never know what you will receive from it just trust it will do what it's supposed to and enjoy the journey...