I started by pretty much combing the web for information before I met some local practitioners and teachers. International Center for Reiki training (reiki.org) does contain a bit of information. You might even find some books on Reiki at a local public library (as I certainly did). Receiving Reiki and asking questions from a local practitioner is a good start, also, but not required.

Reiki is actually a pretty simple form of hands-on healing. To put it plainly, it involves mostly a little bit of believing, a little bit of focusing, a little bit of faith, and a little bit of working with yourself in spiritual development. Mostly what is involved during a formal learning process is a form of spiritual attunement (kind of like opening a valve into your spiritual self, higher energies, higher-self, that sort of thing) that is performed by an instructor, learning a few symbols (some of which may be Kanji characters) which would aid you in focus, and various techniques that could improve your practice. It doesn't get much more complicated to this, though some books on the subject can be quite thick :).

If you got any specific questions about Reiki, feel free to ask. I've studied both the Usui branch of Reiki and Karuna Reiki, so I should be able to answer a few questions in those areas, especially if your looking into formal training.