Overclocking and tweaking help

So I have a decent budget gaming pc and I am completely new to overclocking CPU's, GPU's and voltage tweaking, First of all my pc specs are:
Case: Cooler master Storm Enforcer
mobo-Asus Maximus V Gene
CPU-Intel core i5 2500(not the unlocked version)
CPU cooler-Corsair H60 water cooler
HDD-Seagate barracuda 1TB
RAM-Corsair Vengeance 4X2GB @ 1600mhz
GPU's-AMD HD7770's in crossfire
PSU-Corsair GS700(700 watts)

So I know I should've bought the i5 2500k but this processor was a part of my previous build which I didnt not plan to replace maybe in the near future, anyway Asus Suite II still allows me to tweak my CPU speed uptil 4.3ghz through turbo evo, but ive heard people saying that it is alot more better to tweak things manually through the Extreme Tweaker tab in the Asus bios, now I have no knowledge/experience as to how I should go about with the settings, hence need an explanation as to how overclocking in general is done keeping into mind minimum risk of damage. and yeah my core temps at idle are around 25C and at full load are around 55C, the H60 is working like a charm!