First time overclocker - i7 2600K

I finished my first build a few months ago and am experimenting with overclocking.

MOBO: ASUS P8Z68-V PRO/GEN3
CPU: Intel Core i7 2600K LGA 1155
COOLING: Cooler Master Hyper 612 PWM

I used the ASUS utility to OC; first fast, then extreme. Over the past couple of weeks the computer failed to boot 2 or 3 times saying OC failed and took me into bios where I lowered BLCK Frequency from 105 to 104 and currently is at 103. Other settings are:
CPU Voltage - 1.330
DDR Voltage - 1.35
VCCIO Voltage - 1.05
CPU VLL Voltage - 1.80
PCH Voltage - 1.05
CHA DATA - 0.50
CHA CTRL - 0.50
CHB DATA - 0.50
CPU Ratio - 45.0 4635MHz (For I, nothing listed for II, III, or IV)

My question is should I be doing manual OC from scratch or just let the ASUS utility do it for me? If I should be doing it myself, where can I find a good step-by-step guide for newbies for a stable OC. (I don't want my computer crashing in the middle of editng audio or video!)

Thanks in advance for feedback.