I recommend using the Intel Extreme Tuning Utility or Aida64 for your stress testing instead of Prime95. Also, check this guide out. I'm using it for my OC now. The videos are a little long, but if you want to overclock the right way, you need to do it slow and methodically with plenty of testing.
http://linustechtips.com/main/topic/41234-intel-haswell-4670k-4770k-overclocking-guide/