This is also called an “out of body experience”. The main barrier to this ability is fear. You must let go entirely of emotions by meditating into a relaxed, hypnagogic state. This is being as close to sleep as possible without actually sleeping. Concentrate on one thing, and when other images appear, observe them only. One is nearer to sleep.
When this state is achieved, with eyes closed, investigate the blackness. Light patterns will be there. They will eventually cease as you go into a deeper state of relaxation. As you go into the deepest form of relaxation, awareness of the body and senses will also cease. You will enter an emptiness with only your own thoughts as companions.
The next stage to enter is Vibration. This is where the astral begins as the central cylinder of the energetic field of the body. A mild tingling may be felt, like electricity. Sleep paralysis feels like this when you are calm experiencing it. At this point, you can search this field for energetic parasites. These feel like strange motions or e-motions.
The vibrational state must be controlled. This can be done by mentally pushing waves up and down your body. This takes practice. The goal is to move the waves as by command. Once this is achieved, you are ready to leave the body. Do this a bit at a time. Move a limb through a nearby object and back again, focusing on the astral self.
Once this is done, decrease the vibrational state until your body goes back to normal. Doing this a few times will prepare you for full separation. After entering the vibrational state, think about getting lighter and lighter. Think about floating upwards only, higher and higher with no other thoughts. Another method is to attempt rolling out of the bed.