Reiki has been becoming increasingly popular over the past decade or so, and for a good reason. Reiki, which represents "universal life force", is attainable by all of us. While it's always a good idea to become attuned to Reiki, it's still possible to harness the powers of this "universal life force" to some degree. Becoming attuned an experienced Reiki Master will help you channel those healing energies in a more powerful manner. Masters will attune you to the healing frequencies of Reiki.
To begin learning Reiki, you'll need to at least be attuned to the first level. There are many forms of Reiki, but Usui is the original, and the one that beginners should always start out with. There are three levels to Usui Reiki, and you'll need to be attuned to all three of them separately by Master in order to become a Master of Reiki and teacher yourself.
You can find a qualified Usui Reiki Master around your area and visit him or her in person, or you can become attuned distantly by an online teacher. It's believed that Reiki is so powerful that it exists outside of "time" and "space", so it can therefore be sent distantly without actually being in close proximity of the Reiki Master.
Either way you choose to receive your Usui Reiki attunements, you can practice healing your pets, friends, or yourself. You can even draw the symbols on your hands when you first start out so you can remember them better. Visualize a light coming from the symbol on your hand (work with each at a time) while you're healing someone or an animal.
After you receive your final attunement, you can be a Reiki Master yourself! You can share the Reiki attunements with others as well as heal. You can even go on to study other healing systems to expand your knowledge. Good luck in your endeavors!