Overclocking safely and effectively requires a considerable understanding of everything you are doing because every chip is unique. One of my G3258s will overclock to 4.2Ghz, the other one to 4.5Ghz with different voltages, voltage steps, and temperatures.
Googling is, at best, going to give number with no meaning.
The guide I linked to gives you the information you need to get started, and shows you how to find out how good your chip is.
This may be of help too. http://www.ocinside.de/workshop_en/amd_fm2_overclock/
Overclocking is for people who are informed about the process or are prepared to spend the time to become informed.