grounding and protection are always important if you are trying to communicate with spirits, IMHO.
For protection, I do a few different things. My favorite protection is to close my eyes and imagine a white light coming from the heavens and pouring down over me. It covers my head and shoulders and all the way down to my feet. I imagine myself being in this protective light and it goes a bit beyond my body as well, as if I am in an egg. Nothing can penetrate this 'shell' of light to harm me.
I also pray to Archangel Michael and ask him and my guardian angels to protect me from all harm.
For grounding, I like to have my feet planted firmly on the floor and imagine roots growing out of the soles of my feet, and going down deep into the ground.
Eating is also a great way to ground yourself. Eat things that are from the ground--root vegetables for instance is a great way to ground yourself, drinking milk, or eating anything made with these items.
After a reading, if you feel the energy is still around, take a shower and imagine the water cleansing the energy off of you and sending it down the drain, deep into the earth to be cleansed as well.
here are a few sites you can check out on this too:
https://wildflowerpara.wordpress.com/2010/04/02/basic-psychic-defense-how-to-ground-center-shield/
http://www.rescuemediums.com/grounding-and-protection.php
http://www.mysticfamiliar.com/archive/first_steps_in_psychic_development/grounding_protecting.htm
there are also many threads here on AT about ways to ground, center yourself and protection--but not sure you can access it w/o being a paying member--
http://www.tarotforum.net/showthread.php?t=177838&highlight=protecting
http://www.tarotforum.net/showthread.php?t=156190
your best bet, if you do not want to become a full member here on A.T. would be to google these techniques and reading up on it. Then finding what works best for you and making it a practice to do this before doing any reading at all, especially mediumship readings.