Ave!
The only time I´ve succeeded transfering my consciousness to my astral body, was by accident. I know a lot of people (including me) have problems to fully let go of their material bodies while doing OOB workings, so I´ll tell you how I succeeded. It might come in handy for someone else.
I had trouble sleeping one night, so I did a basic relaxation "ritual" (the one mentioned in Modern Magick, by Kraig). After I had reached total relaxation, I just lay there and let my mind go where it wanted. After about 20 minutes I suddenly rememberd an interesting relaxation technique, which I found in a article about hypnosis. The technique is to tell one self that "I don´t need my feet now, they are useless to me", and visualize your feet dissappearing. Then your legs, torso, arms etc.. When I only had my head left (feels a bit freaky when you are only a head on a pillow
) I did the same thing with it. The instant my head dissappeard, my astral body (which I wasn´t aware of until then) almost violently pulled itself up in the air, finally free from my physical body. This did not last for long, because I was so surprised of what just happened that I lost controll of it and I became aware of my physical body again.It seems that the combination of theese two relaxation techniques are pretty effective, at least for me.