Often called the forefather of Greek religion, the Mycenaean people laid the groundwork to what most Greeks would begin to worship. With them being considered the first Greek city, or at least the first to speak the Greek language there religious texts and practices served very important for the future of Greece. The ancient people of Mycenae are proven to have practiced polytheism, or a worship of many gods. With there being a lot of proof for them to have worshiped Greek gods such as Zues, Poisiden, Athena, etc. Most of the religious artifacts available for research today are in the forms of clay tablets written in linear B a precursor to the Greek language. Whom exactly was responsible for creating these tablets is unknown. However within clay tablets lies evidence to prove that the Mycenaean worked parts of christianity into their religious beliefs. Along with many small parts of tons of other religions. Which like most of Greece makes them a syncretist society that tied a variety of religions into their beliefs.
Many historians believe that the people of Mycenae practiced animal sacrifice with a lot of speculation (albeit not confirmation) about human sacrifices. There were many sacrifices made to Zues with tablets suggesting that they were often made after times of calamity. We can thank our knowledge of this to archeologists who were able to find a plethora of animal bones near the religious areas. Interestingly there were also some human bones found, which has started debates throughout historians about the Mycenaeans sacrificed humans. But it is important to restate there is no definitive evidence in ancient text or archeology to prove that this behavior was exhibited.
Other religious practices include common ones like burying their dead. Which started in deep shaft graves but later evolved into large tombs dug into hillsides. They were one of the few cities in ancient Greece to put the dead in tombs. The dead were often buried with their families and possessions like their own material possessions, valuables and masks made out of gold or silver on their face. Myceneans performed offerings and prayers to their gods in certain places of importance. Overall the Mycenaean religions did not vary much from ancient civilisations at the time but did lay the blueprint for religion in Greece along with possessing its own unique traits.