All ancient cultures had sacred geometric designs representative of their Gods, which had a mantra (or sacred sound vibration) that corresponded to it. In the Vedic culture, we find much power and energy said to be held within sacred geometric symbols. Yantras are not "lucky charms" to be worn or displayed as icons of power in and of themselves. Much specific knowledge and ability must go into their preparation and much dedication and worship is required to achieve the desired effects.
Yantra means a "talisman", or "instrument" or " Amulet" or "Kavach" which, if prepared and created by a qualified person as well as utilised under his specific instructions for fruitful results, will help to gain the objector objects of desire or ambition. Although it would not be a difficult task for most of us to copy the form of a yantra, it would not have the desired effect. Furthermore, to be perfectly honest, it would be all but useless if not created by a qualified person and then "infused" with the specific energy via the medium of mantra. Otherwise, it becomes just an interesting form or picture to look at, but has no real effect on time or circumstances within life.
Yantras should always be used on the level. If drawn on paper the colours preferable are red, orange, yellow or a combination of these. A Yantra without bija mantras is dead. They can be drawn to whatever size is required. In worship they should be placed level on a pedestal or pitha. Before any Yantra is a suitable object for puja, it must be given life (pranapratishta).
A Yantra is essential in every field of your life, to attain success in your profession, to acquire wealth, to win in court cases, to ward off diseases and to progress in meditation. By having a Yantra and keeping it in a sacred place in your house, gazing it everyday can fulfill your desires and help in attaining your goals.
There are different types of Yantras for different purposes. They can help you to attain success in your business, bring the person under your control, and bring wealth and prosperity to you. The Yantras have to be purified and energized before using it. Yantras energized during the nights of Maha Shivratri, Holi and Diwali are most effective and powerful. Normally the related Mantras are also chanted in the presence of the Yantras for quick results.
It is auspicious to see the Yantra daily in the morning and one should lit incense/dhoop or lamp with ghee before the Yantra every morning. By doing this the native is blessed with success and wealth. We send these Yantras only after Pran pratishta (energising or performing Pooja on them).