The majority of the people are Hindus and Hinduism is the strange amalgam of differing beliefs, some even contradictory. But most believe in the holy word, the Om. Jainism, Buddhism, Sikhism are also called the Om kaar religions because they too believe in the sanctity of Om. The river Ganges is held sacred and Varansi is the holiest of the holy centers.
It is believed that Hinduism developed as a result of the mixing of the Dravidian and Aryan influence. Hinduism is the world's third largest religion after Christianity and Islam but uniquely it has no single founder, no church hierarchy and no central authority. One cannot become a Hindu; you have to be born to the faith. Therefore there is no proselytizing like Christianity or Islam.
There are about 330 million deities in Hindu religion at last count. You might be bewildered at the numerous changing gods and goddesses from region to region but for Indians all these don't make much of a difference because they know under the pictures the spirit is the same. Hindus revere the four Vedas, which have an antiquity that goes back to the fertility rites of the Dravidians and the nature worship of the Aryans.
The Dharma Shastra were more in use by the lay people. These are basically codes of moral and social conduct and describe the various obligations of man according to his status in life. The most important religious epics for the Hindus are the Ramayana and the Mahabharata, the longest epics in the world.
Hindus have a number of religious festivals like Deepawali, the festival of lights, Holi, the festival of colours, and Ramanavami, the birthday of Lord Rama, the idealized God. Another major festival is Shivaratri, the night of Shiva, the god of dissolution, for the Hindus believe life goes round in a circle and everything ever made must be destroyed for the next round of creation to start again.
Hindus pray in temples and only some temples will allow a non-Hindu to come in. Anyone who is not a Hindu cannot participate in Hindu praying rituals at temples. Some may allow you to watch, especially if you with a friend. You must not touch anything in a temple since Hinduism believes strongly in pollution and non-pollution.
Organizations like the Chinmaya Mission are very open and will welcome you to sit in at their lectures. Their books are simple and extract the essence of Hinduism. The Art of Living of Sri Sri Ravishankar, which is a worldwide organization, is also a good place to learn about Hindu religion and participate in its bhajans or community chanting. You can pick up CDs of Hindu prayer chants of the other Ravi Shankar, of Beatles fame.
Ganesh is a favorite god who is talismanic and is found in cars, shops, hotels, and houses everywhere since he is supposed to be a destroyer of obstacles as well as a destroyer of undesirable forces within oneself. It is a good idea to carry back with you small talismanic icons of Ganesha in crystal, silver or even in jade and amethyst.
You will find an unbelievable variety of substances out of which Ganesha is wrought. Joss sticks and lamps play a great role in Indian worship. Joss sticks in wonderful organic essences are used ritually for worship.