Answer:
Meditation. Somepeople go to the astral plane on accident in their sleep.
An easy way to astral project is to meditate and imagine yourself on a swing. Swing high and eventually jump off the swing. When you land, you will be in the astral plane. This will take a few tries, so dont give up if you dont get it the first try or fall asleep. You will know if your in the astral plane. You may feel like you are in a dream, but will also feel like you are awake.