There is a special type of concentrative meditation which we will call 'Chakra meditation'. This is basically Kundalini yoga -- the practice of causing psychic energy (kundalini) to flow up sushumna, energizing the various chakras along the way. The practice, considered dangerous by some, will produce definite physiological sensations and psychological effects if continued long enough. It should not be attempted by epileptics or persons with an unstable mental or physical condition, or with heart disease. Certain drugs and medications, such as those used to treat epilepsy may retard progress. Although the technique is very simple, it may eventually produce powerful results. Results may at first appear hours after the practice during sleep. As each chakra is energized by this practice, it is said to add occult powers (sidhis), until at last the crown chakra is reached, and with it, full enlightenment is attained. Sometimes kundalini awakens all by itself.
To practice this chakra meditation, you simply concentrate on the chakras, beginning with the root chakra, and moving progressively up, as you visualize psychic energy from the root chakra traveling up shushumna and vivifying each higher chakra. As we mentioned the chakras have certain properties associated with them, so that this type of visualization may 'raise consciousness', promote astral projection, and other things -- once you have reached ajna and eventually the crown chakra. You might typically meditate in this fashion for 15 minutes to a half hour a day.
It might help to practice some hatha yoga or other physical exercise in an effort to make the spinal cord 'more flexible'. Diet may also affect the process. The technique is also similar to the Tibetan 'Tummo' meditation. The rise of kundalini is sometimes experienced as a 'vibration' or buzzing, as light, or as heat.
~ from Maat's Book of Shadows