Yoga nidra meditation is a type of meditation practice in which the practitioner consciously relaxes the muscles in the entire body to achieve a physical feeling of calm and relaxation, as well as feeling it in the mind. Typically, yoga nidra meditation is begun with the practitioner lying flat on his or her back, in the yoga posture known as savasana, or corpse pose. Then, the individual begins breathing deeply and brings his or her focus to the legs and feet, relaxing those; then to the lower back, relaxing those muscles; and so on up the body.
Some people choose to end a yoga practice with yoga nidra meditation, while others will simply do this meditation as a standalone practice. There is no right or wrong way to do it. It is extremely helpful for relieving stress and anxiety, increasing awareness about the body, and entering into a state of profound relaxation. The goal of yoga nidra meditation, or any meditation, is certainly not to fall asleep, though some people do use this practice to unwind in bed at the end of the day and achieve a more restful night's sleep.
As with other meditation practices, learning yoga nidra meditation can take some time and patience, as well as persistence. It is very difficult to quiet the mind and target the concentration in specific areas, and to relax certain muscle groups. It is important not to get frustrated, and to just to gently bring the mind back to the practice if it wanders. To begin, simply lay on the back with the legs spread slightly apart, and the arms at the side with the palms up. Direct the awareness to the feet and the lower legs first, and try to identify each of the muscles and consciously relax them.
The point of yoga nidra meditation is not to rush through the practice, but to really focus on feeling each muscle and the points where the body is touching the floor. As each muscle is relaxed, continue directing the awareness to muscles throughout the entire body, including the abdomen, back, and arms, all the way up through the neck and throat. Some people then begin again and head back down the body, more deeply relaxing muscles in the chest, then the abdomen, then the legs, and so on. It is possible to find audio versions of instructions such as these, which will name each area of the body to focus the awareness on throughout the meditation; this is helpful for some people who find their concentration wanders, who or aren't sure where to go next.