The couple things I can think of to remember is run to
-Turn off turbo boost
-Adjust your CPU base clock frequency to 100 MHz
-Manualy adjust your core clock ratio/multiplier starting at 38x or 40x
-Adjust vcore manualy to 1.1 or 1.125 for starters
Gigabyte UEFI if voltage is left in auto will apply voltage far too aggressively and result in a massive amount of heat at a low overclock.
From here stability test, and if all looks good add more multiplier, otherwise add voltage in .01 to.05 volt steps until you get stability then add multiplier and repeat.
For haswell design temp is 90 degrees so try not to get above low 80's while stress testing. 70's is better if you can manage.