Meditation, breathing, and patience. I've noticed that most people tend to not give off much at all, but a seasoned martial artist or yoga/chi kung master puts out like a torch. A shidoshi I had the honor of training with back in Florida gave off an aura that I could detect under a mid-day sun (we always trained outdoors), and I consider myself the lowest of noobs when it comes to this esoteric stuff. I've read that pregnant women can give off quite a show of colors, although I've never experienced that myself.
In the 60s, we had the kung fu craze. Legitimate sifus were outnumbered easily by frauds mimicking what they saw on TV. In the 70s it was karate, in the 80s ninjutsu, in the 90s it was Brazilian jujutsu. Authentic teachers more concerned with teaching rather than class fees were pretty thin on the ground. I'm not sure if it has something to do with the 'New Age' fascination America is going through (Self-Help, Shiatsu, Feng Shui, Dr. Phil, etc) but now the internal breathing arts of China, Japan and India seem to be enjoying a measure of attention similar to the fads of earlier decades. A wary word to any curious explorers: there's a lot of cons out there.
*steps off soapbox*