Before sleep each night begin saying the Bija Mantra for your Ketu according to the Nakshatra. If Ketu in Ashleesha nakshatra you would say "Puuh" for Nagas. If your Ketu were in Jyestha you would say "Lam" for Indra .If Shatabhisha, then "Vam" for Varuna, etc. This has a subtle effect on a person, similar to anesthesia, in that it immediately begins causing a person to withdraw from their senses. If you have meditated before or said other mantras, you will most likely find that this Mantra produces the most startling results for quieting the mind, and many experience it almost like a thick black veil coming over the eyes a few minutes of saying it internally. This is the state you are aiming for, which is what it feels like to pull your Yin chi up and leave your body. You will also learn to pull your Yin Chi over your eyes easily while you are awake in order to see non-physical entities. As with anything regarding Ketu and the personal Demon or Daemon of a person, they must be careful in regards to deception, as one's past Karmas and illusions can easily overwhelm a person due to Ketu stirring up the older layers of a person from previous lives. This is why saying this mantra often causes past life memories to surface very quickly. The dangers of Ketu are the dangers of the astral plane in general, which are related to falling under the glamor, illusions, and temptations of the Astral plane itself. We cannot avoid activating our Ketu if we desire true Gnosis or experiential knowledge, however, and so we must take proper precautions before our Astral explorations which are as follows:
1. Record every session even if you feel nothing happened, as many times your astral body simply did not transfer the memory to your concious mind and you do not remember. The record is important as it is an extremley disturbing experience to begin uncovering patterns in one's journals which show flaws, defects, and even the influence of negative entities on one's self... which occur as one attempts to grow spiritually. If you do not keep a journal, you open yourself to many dangers.
2. Choose a destination or location and constantly direct yourself mentally the entire time. Every trip must be totally willed from beginning to end. A person can choose a tarot card or even the realm of the mantra itself (recommended) and begin observing the environment that unfolds before them. Record all that you see after your trip. This is the way to obtain any and all information about a given symbol. The easiest to begin with is observing the realm of the nakshatra of your Ketu by saying the bija. Once skill is obtained, you may investigate any nakshatra, symbol, or tarot card etc that you wish.
3. For one hour a day, vocalize the vowels I, E, O, U, A, M, and S while taking a deep breath and expending all of one's air on each vowel. Iiiiiiiiiiiiiiiiii inhale* Ehhhhhhhhhhhh* inhale Ohhhhhhhhh *inhale etc, etc. This is very important, as this performs the exercise known as "rising on the planes" automatically and teaches a person's astral body how to do this while a person is asleep. If you do this for an hour a day, you will find that you dream of performing the exercise and this is very good as it works to slowly develop the astral body to its fullest extent. It also programs the astral body to better defend itself and energizes it with more power. This exercise is vital for learning to call elementals and spirits as well.
Anyone who practices these exercises becomes a member of the astral school of adepts, the church of experience/gnosis, and can ask to travel to it before sleep to be instructed. They will be taught and tested accordingly and to their capacity and sincerity.