At the Dark of the Moon

Introspection, trance work, self-evalution

Dream work

Fast or eat sparingly

Don't overwork

Wrap yourself in a covering or veil of some kind, arranged so you can breathe properly (oxygen deprivation is not an essential part of the experience.)

I especially like some slow and evocative sound for this--Tibetan temple bells, for example.
Close your eyes and go into a cave. As you go deeper in, the light becomes fainter and fainter, and you have to feel your way with your feet and hands.
The passageway becomes narrower, and more difficult to negotiate. You go deeper and deeper into the earth.
Then after a time you will suddenly lose your footing and go floating in free fall, around and around, down the passageway, until you land in a cavern deep inside the earth.
There you may find something, or you may meet someone.
You may be told something you need to know, or you may be given something to take back with you.
Perhaps you will find or be given something that must remain in the cavern, but which you can return to again.
When you are ready to leave the cavern, you will find that you can float up and out the passageway, by the same way you came.
Then you will find your footing, and make you way along the passage, feeling with your feet and hands, until you return to the mouth of the cave.