Entrails were taken from animals that were commonly sacrificed at the various temples, and often entrail readings were taken during these celebrations just before the meat from the sacrifice had been distributed to the celebrants. This allowed the ritual leaders to know if the sacrifice had been accepted or not. One theory developed by the Stoic school of philosophy for why the Gods spoke through the body parts of slain animals was called “sympatheia (συμπάθεια)” 2. Sympatheia asserted that the divine realms and beings were connected to every part of creation, including the animals being led to the knife. This connection left marks that could be discerned and interpreted because divine entities’ greater movements would affect smaller things and beings on Earth. The liver tended to be the organ of choice, but the Gods might motivate a diviner to a better organ during the reading.3 Abnormalities of the organs were considered extremely important messages and a single organ could be divided up into different segments which would have specific meanings.
“The birds of clearest omen were the great birds of prey--hawks," Apollo's swift messengers," and eagles, "the birds of Zeus." It was a good omen if the birds flew from left to right, a bad omen if in the reverse direction.” 6
Perhaps it is because birds fly in the heavens, and are thus closer to the Gods than land bound humans, that they were considered by Cicero and other writers as the most important means for the Divinities to communicate with the mortal world.7 We do not have a list of specific rules which the Auspice would use to judge what exactly the Gods were trying to say by sending a bird flying by. We do know from Roman and other nations that used Oionomanteia, that an Auspice would be required to stand and look in a particular direction when he surveyed the sky. Noises the birds made, or how they flew would also affect how the omen was interpreted.
“We do know, however, that Greek oionoskopeis distinguished between right and left, with right generally being positive and left negative.8 .
Biblioteca Arcana has also provided a way for the dice throws to be tied into a Greek alphabet oracle by modern users of this system of divination11. The numbers as added up after the dice are thrown are assigned a letter value. Each letter has its own interpretation based on poems and other Greek writings.
1 Mapping the Entrails: The Art of Greek Hepatomancy by Derek Collins. http://apaclassics.org/images/uploads/documents/abstracts/collins_1.pdf
3 Ancient Greek Divination by Sarah Iles Johnston. John Wiley and Sons Ltd, The Atrium, Chichester, West Sussex, UK. 2008. p.127
4 Reading the Birds: Oionomanteia in Early Epic by Derek Collins. Colby Quarterly, Volume 38 Issue 1 March (2002). ( http://digitalcommons.colby.edu/cgi/viewcontent.cgi?article=3362&context=cq&sei-redir=1&referer=http%3A%2F%2Fwww.google.com%2Furl%3Fsa%3Dt%26rct%3Dj%26q%3Dgreek%2520entrial%2520reading%26source%3Dweb%26cd%3D10%26ved%3D0CGQQFjAJ%26url%3Dhttp%253A%252F%252Fdigitalcommons.colby.edu%252Fcgi%252Fviewcontent.cgi%253Farticle%253D3362%2526context%253Dcq%26ei%3DzE1JULz4LaebyQH494C4Cw%26usg%3DAFQjCNH_Kz5uRnfs-5Oq9g69j_LhNeYnoQ#search=%22greek%20entrial%20reading%22
6 “A Day in Old Athens,” by William Stearns Davis. p. 186 (1910)
7 Johnston. p129
8 Johnston, p. 129
10 Johnston, p.9911 http://web.eecs.utk.edu/~mclennan/BA/GAO.html