Yoga nidra or yogi sleep has been used for thousands of years by yogis. In the Upanishads, there are three states of consciousness: waking, dreaming and deep sleep. Yoga nidra allows an individual to leave the waking state, move past the dreaming state and into deep sleep while remaining awake or conscious during the whole process. In yoga nidra, there are no dreams to explore. Instead, it is a process of emptying. It purifies the deeper aspect of the human mind by exploring deep impressions or samskaras. This is essential as samskaras drive our karma.
To develop your clairvoyance, you must be able to attain a higher level of consciousness. You need to work on your spirituality and this can be done in several ways. The most common way is through tapping the power of your third eye. Another effective way is through constant meditation.