The FX-6300 is a great overclockable CPU. Do you have an aftermarket cooler as the stock isn't capable of a decent overclock.
Read this article -
http://www.overclock.net/t/1348623/amd-bulldozer-and-piledriver-overclocking-guide-asus-motherboard
Start small by keeping the voltage at stock level and just push the multiplier up to 4.2ghz.
You want Prime95 and HWmonitor for stress testing and temp monitoring. You just adjust the bios and then run a small FFT for 10mins keeping an eye on your temps. If no cores fail or you don't get any BSOD's or crashes you can keep pushing the clock multiplier higher.
I personally with my FX6300 OC'd to 4.2ghz at stock volts and my temps never went over 62c (the advised max for your CPU).
At the minute I'm running at 4.4ghz with a Coolermaster Hyper EVO 212 (a very capable but budget cooler) at 1.4v temps do touch 65c at 100% load but never go over 50c in gaming.