I have been trying to increase the frequency and "at will" factor in my OBEs. Sometimes I'll get so relaxed I'll fall asleep. Other times I'll just end up in a meditative state without the initiation of an out-of-body experience. I have been actively pursuing what I once had down to a bit more of a science when I was younger. Although the frequency of my OBEs has increased during the couple of years or so, I recently came across this technique at World of Lucid Dreaming and I've found it extremely helpful, called "Stop, Drop & Roll".
This is one of the best techniques I've found to date, and I've read a few books on the subject. At the essence of the technique are steps needed to be taken to trick the physical body into sleep paralysis. The missing key for me was the resistance of what are known as urges that the body uses to make sure the mind is asleep before initiating sleep paralysis in order to enter the dream state. I've had a breakthrough the first couple of times that I used this, most notably resisting what is known as the roll-over urge. My energy/astral body has turned on relatively quickly within thirty minutes while I've remained awake. Remaining awake - the mind - and avoiding this urges that trigger sleep paralysis, has been much more effective than relaxation techniques and visualizations alone.