Honestly, I don't. It's not something I really practice. But, one could find information in books (peer reviewed would be best) on Greek and Roman divination. The Greeks looked at the flights and cries from birds for signs, and the Romans performed this under the state religion's Augury. One could also read up on some ornithology. Also, start actually bird watching.
A look at Greek divination as a whole can be found in Ancient Greek Divination by Sarah Iles Johnston. It's a good read.
Other than that, perhaps someone knows a more closer to home method for this type of divination?