Why 'Namaskar' and not a 'hand shake'?

While visiting places of worship and viewing the Deities or after meeting a elderly or a respected person our hands are automatically joined together in Namaskar. Namaskar is a sattva predominant impression on the Hindu mind, an action that maintains the rich heritage of Hindu culture. Namaskar is a simple and beautiful act of expression of divine qualities like devotion, love, respect and humility that endows one with Divine energy.
Nowadays, perhaps due to ignorance about the Science of Spirituality or the increasing influence of the western culture, many people shake hands.

Why is it not appropriate to shake hands?

In short, in a handshake, the raja-tama components in one person may get transferred to the other person, thereby lowering his sattvikta (Purity levels). While practicing Spirituality, our objective is to perform acts which increase our sattvikta.
If at all they do Namaskar by joining their palms, it is done just as a formality. As the act is not based on faith, the benefit derived from it is minimal. Along with faith it is essential that every religious act be correctly performed according to the Science of Spirituality, so that it gives complete benefit. In this series, as with the others,  along with information on various methods of doing Namaskar, the Science in them is also explained. Understanding the Science will help in strengthening faith in the act. Such an act correctly performed with faith, will yield corresponding benefits.
Mistakes made while doing Namaskar counter its benefit. Hence incorrect acts that need to be avoided while doing Namaskar are also mentioned in this series, with the scientific explanation. Similarly, guidance has been provided on who not to do Namaskar to. We make this prayer at the Lotus Feet of Shri Guru - 'Let all imbibe the methods of doing Namaskar mentioned here and hand them on to the future generations.'

Q. How does one do Namaskar to an individual of the same age group?