I perform circular breathing techniques. For instance, I will sit upright, comfortable and cross-legged, with my hands resting lightly on my knees. For four seconds, I breathe deeply through my nose, innervating my upper chest with fresh and restorative oxygen. I hold that fresh air in my upper chest, allowing my chest to expand and promoting the oxygen diffusing in the capillaries of my lungs, for six seconds. Then, as though I were blowing out a candle, I slowly exhale all of the air out of my mouth until my lungs are essentially empty - usually for 10-12 seconds. The key is to exhale slowly.
So if you think about it, it is circular. In the nose, hold in the chest, out the mouth. In the nose, hold in the chest, out the mouth. I can induce trance-like states with this simple technique.
Another technique I have recently found very helpful is an app on my iPad called Hypnomaniac. The session for sleep-induction is wonderful.
Binaural beats may be yet another option for you, too
~ Vaya