Even for advanced meditators, holding the body perfectly still can be difficult. I have been meditating for over 13 years now and there are occasions when I still find it difficult. However, if you understand the purpose as stated in the advice given above, it provides a stronger will to hold still.
There are many methods of meditation being taught and most of them are very good. This particular method taught by Paramhansa Yogananda is the original yoga method taught by Sri Krishna over 5,000 years ago. You can find specific assistance in my "Meditation/How to Meditate" and "Meditation/Hong Sau Meditation" web pages. For further assistance, please go to the Ananda Meditation website.
It is important to develop a routine for meditation. Try to select the same time every day, twice a day if possible. Sunrise, before the family gets up is ideal. Sunset is also an auspicious time. But any time is better than not meditating at all. In the beginning you do not have to meditate long. Yogananda said that it is more important to meditate deeply. Once you get used to going deep, you will find that time has no meaning and you will be meditationg longer