A discussion of religious practices in ancient Greece is necessary to distinguish the aspects of religion separate from the telling or understanding of myths. Many rituals and practices come from myths, and they are generally performed as a way to communicate with the gods: to ask them for something, thank them for the occurrence of an event, gain their general good will, or attempt to read messages or warnings that the gods have sent.
A large part of ancient Greek religion is sacrifice and persuasion. The ancient Greek people believed that they had to sacrifice to the gods to convince them to help them with something. They would often sacrifice again once the gods met their request to thank the god and be sure that they would listen again the next time they were asked for assistance. Each of the gods are related to their own sphere of influence and power, so the Greeks would pray to the god of whatever they wanted effected; e.g., you might pray and sacrifice to Venus if you wanted help in love, or to Mars if you needed victory in warfare.
Animals were the usual sacrificial victims. Cattle were a common sacrifice, but also an expensive one. The animals were brought to an altar and the officiating priests would wash their hands to purify themselves and sprinkle grain seeds on the animal to purify them. The animals’ heads were lifted to the sky, and a hidden sacrificial knife was used by the priests to kill the animal. The fat of the animal was wrapped around the bones and burned. It was believed that the smoke would float up to the gods, and they would enjoy the sacrifice in this way. A myth about a titan named Prometheus—an immortal, god-like being—explains how he tricked the gods into choosing this part of the animal for their own. The meat was then roasted and eaten by the attendees. Meat was very expensive, and this was the only time that many Greeks would eat meat. This was a rather common occurrence, however, for there were many festivals in Greek religion where public sacrifices would take place to thank or pray for the gods` protection, a good harvest, victory in war and other public concerns of the community.