to consciously astral project, you have to cause your psyche to be awake while your body is fully asleep. the body (as opposed to the psyche) must fall right below the sleep threshold versus remaining right above the sleep threshold. it's essentially the opposite of meditation where a person tries to stay physically awake while relaxing the psyche.
sleep deprivation and/or fasting may be the most effective method to get your psyche into a wake-dreaming state (ideally coupled with sensory deprivation for amplification purposes), afterwhich the body will eventually fall into a very deep sleep. it's okay to physically fall asleep if your psyche remains very active. you want your psyche as active as possible with your body as passive as possible. again, it's the exact opposite of meditation where people try to relax the psyche but stay physically awake.