The Aryans believed in many gods. They worshipped Indra, the god of war; Agni, the god of fire; and Usha, the goddess of the morning, as well as many other minor gods and goddesses. They believed that these deities had great power over their lives. The priests performed elaborate ceremonies in an effort to both please them as well as gain their favor.
Over time the Aryan religion slowly evolved, becoming more complex and rich with tradition and ceremony. The religion grew to become Hinduism, which is one of the primary religions still practiced in the region today.
The truth of the matter is that you always know the right thing to do. The hard part is doing it.