Face North or NorthEast (though any direction will do if you can visualize well).
Clear your mind (a relaxation ritual can be done before hand to enhance the effect) perform the Fourfold Breath (inhale on a count of four, hold your breath for a count of four, exhale on a count of four, hold a count of four) your mind should be totally clear, you will reach a state of gnosis. Breath control is very important throughout this exercise.
The next part is to project yourself, not so much astral, but more as visualization. The projection should coincide with your exhalation. Let the palms of your hands face the ground while saying something like "The stability of the Earth below me". Project your consciousness to the center Earth visualize all the layers to the molten core. All of this takes only a moment. Then draw the energy of the Earth element into the Heart Chakra.
Next raise your arms above your head and project yourself beyond the stars. Absorb the pure energy of the universe and say " The Stars above me". This will connect you with the Air element and stellar inspiration.
Bring this all back to yourself combining the stellar energy with the Earthly force that you already present. If you are successful you will feel the centering in a big way! You will feel taller, and very aware of physical objects and living things well beyond your physical self.
Your arms still above your head reach out to the right with your right hand towards the East or SE, and visualize the Morning Sun, and say "The Sun Rises to the East....," bring the element of fire into yourself, then reach out with the left arm to the left and say "....The Moon sets into the oceans of the West" now bring the element of Water into yourself. Bring both hands to cross in front of your heart combining these energies into a calm center feel the hum, and say "And I am Chaos". You may want to repeat "I am Chaos". From here you my do any ritual you desire.