You can also meditate standing within the Tree, so that your feet at at Malkuth (Earth), your pelvis is at Yesod (Moon), heart is at Tiphareth (Sun) and so on. You must “Cross the Abyss” (Daath) so that your head is just below Kether whose symbol is appropriately enough, a Crowned King.
This is a huge topic that entire books have been written about, but these little keys can help you go through the doors on your own. It is the basis of Tables of Correspondences, relationships between powers and deities, and many other things. It is very enlightening to take your favorite Gods, say the Greek Gods, and put each one in a sphere according his or her planetary association and see how the energies collide and interact. You can understand things at a much deeper level when you play with the Tree of Life in this way.
Also try this free pdf e-books:Frater Astrum - Temple Of Flame The Ritual Opening Of The Veil
Austin Osman Spare - The Book Of Pleasure Or Self Love
Paracelsus - The Treasure Of Treasures For Alchemists