Roman Prayer
Roman's celebrated and prayed to their gods by holding festivals. Often times because their gods were so numerous the Roman people themselves would forget what a specific god did. For example, every year the Romans would hold a festival on July 25 for the goddess Furrina. Sadly, by the middle of the first century BC, there was not a single person who knew who Furrina was or what she did even though they celebrated her every year. Sacrifice usually came hand in hand with prayer. Sacrifices were so important that if a single mistake was made the entire process would have to be repeated. Animal sacrifices were popular and often bloody ordeals. The sacrifice itself was done very elaborately. First an animal would be chosen depending on the god that the sacrifice was for. Then the beast's head would be sprinkled with a mix of wine and bread baked by the vestal virgins. Then the poor animal's throat would be cut to kill it. It's innards would then be thoroughly checked and inspected to make sure that the animal was a proper sacrifice for their gods. If something amiss was found in the animal then an entire new animal would have to be selected and the process would begin all over again. After the entrails were removed and everything seemed to be alright, all the important organs would immediately be burned on the alter. The meat of the sacrifice would be saved and would usually be eaten for a feast. After the organs were burned a priest began whispering prayers. His eyes would be covered so he could see no evil and a flute would be played so he could hear no evil. Because of the needed perfection for the sacrifice and the somewhat high failure rate, sacrifices were logically never made before a big event or gathering for fear that the gods would be angry at the failed sacrifice and incur their wrath upon the gathering.
http://www.roman-empire.net/religion/sacrifice.html