Everyone has pretty much given the information to start. Doing a little research and buying some books will help your knowledge. Also, my Reiki master had told me that its also good to gain the experience from Reiki sessions. Find a reiki master or practitioner and have some reiki sessions done on you to gain some first hand experience and healing. The healing will really help. After you go through some sessions and understand the basis of the healing system you'll be better ready. Trust your intuition too. Let guide you into knowing when you are ready.