I admit I don't consider myself a New Ager, per se. I am not easily swayed by claims of alkaline water and magnets in bracelets and the like, but I am a huge advocate of permaculture, sustainability, organic growing, and healthy living.
I came across a very simple and very nicely presented video teaching the basics of Reiki and how it works and demonstrating. It is very impressive and Randolph Shipin did an excellent job. In fact, you can find him at these two sites and I encourage you to go give them a check.
The concept of Reiki is healing through the use of channeled energy. Although it certainly has its skeptics and the use of the word "energy" with a flair of generality is used often in New Age practices, there is something to be said about two people focusing on a person's balance and health, healing and belief.
Stress is the worst antagonizing force on our bodies and the opposite of stress is peace. Any time a person who believes is met with a person who proclaims to heal, a sense of peace occurs. These effects and perspective change can help a person to go through their day feeling aligned, protected, and healing. That counters stress and its oxidizing effects.
So, whether you believe a person can heal or not, any focus of centering, meditation and relaxation is hugely beneficial. Many believe that Reiki has healed them of emotional and physical issues. If it works, does it matter why? Some don't understand how aspirin works and yet it does.
Reiki isn't the only way to seek some healing; massage, meditation, prayer, sweat lodges, vigorous exercise, petting a dog, watching a sunset, all these things evoke the healing. The key is taking time each and every day to have that centering and perspective shift so you can go out and handle more life.