Herodotus, the “Father of History,” is one of the most used ancient sources- for better or worse. His Histories, written in the 5th century BCE, seem to have answers for everything. Here are a few guides for those new to Herodotus:

Taking Herodotus Personally
P. A. Cartledge
The Classical World
Vol. 102, No. 4 (SUMMER 2009), pp. 371-382

The Historical Method of Herodotus
Donald Lateiner

Herodotus
James Romm