Prostrations are the approved exercise of the architect of the human body for the strength to break down the ego for service to others. Brahma designed the body to enjoy this beautiful and expansive universe and to be useful and helpful to its inhabitants. According to the Sacred Text, full body prostrations are an important morning exercise for keeping the body trim and fit. I have translated many mantras that describe the virtue of doing them, but none that describes how, so here is one way.
In the early morning before sunrise, stand with the feet a little apart and inhale a breath through the nose as you raise the hands high above the head as if reaching to heaven for God. Begin exhaling from the mouth as you lower the arms to bring the palms together at heart level. This can be a position to stop in when tired, but most of the time it will be momentary. The hands separate, and as you come to a kneeling position, place the palms on the ground a few inches to a foot in front and a foot or so apart. Extend the right hand forward about a foot and a half to two feet, then the left, and finish exhalation while lowering the body to the ground. Swing both arms forward, stretch out the body and touch the forehead to the Goddess, Mother Earth. Begin to draw in the breath as you draw back the hands and push the upper body off the ground. Step back with the left hand, then the right until they are in front of you and you are kneeling, stand upright, and raise the hands high above the head and reach for God. That completes one prostration. They can be repeated any number of times, the Veda says ninety-nine to stop the flow of venom.
In a weeklong meditation retreat, one of the skinniest gurus in the world challenged us students to a prostration contest. His assurances of proficiency coupled with our struggles assured him of no takers amongst us. It was funny, but seriously, prostrations done first thing in the morning and their purpose is clear by the extra energy during the day. Prostrations are a virtuous activity to engage in with countless ways of enjoying. Some religious practitioners prostrate the entire distance to a Sacred Shrine, or around the site. The Creator urges one to wake before dawn, go anywhere, and prostrate until the body is glistening with sweat and roaring filling the belly with the breath. That gives a body a nice warm glow for sitting down in the sun to praise with light.
Addendum: About five years ago, I began experiencing knee issues, not related to prostrations, but caused an end to the practice. However, through caution and care, the knees have improved, and I am now in the practice again with a modification. A breath inhaled to reach to heaven, and exhaled to touch the earth, is repeated twelve times. The twelfth time, come to a kneeling position before stretching out on the ground. Draw back the hands, breath normally, and complete twelve push-ups before returning to a kneeling position, standing and reaching to heaven. Ninety-nine times to stop to flow of venom.