Every night when you go to sleep you experience an OBE, but you just don't realize it.
As far as how to do this while conscious, this is not necessarily advisable or beneficial to have as an experience. It is not going to happen simply because you want to do it.
It is best to begin this path, if you really wish to have the experience, by learning more about the soul aspects of your existance.
It is just as important to be fully present and grounded in life as it is to be able to leave your body completely. It is best to have mastered conscious awareness of yourself within the physical realm where you reside in a body before attempting to detach from it.
And always it is best to ask yourself why you wish to have the experience of astral projection. If it is just for fun, you might find it more interesting to ride a roller coaster!
Peace!