to start with drop your memory speed to its lowest it will go for overclocking the cpu.
up the FSB frequency in 25mhz steps until it becomes unstable, add 0.1volts on the cpu, add more fsb until unstable, up the voltage etc. dont take it past 1.4volts and make sure your temps dont go much above 65-70 under load. when your happy with your overclock, test it properly with something like OCCT to check stability and temps. If it fails then add a little more voltage to stabilise it.
only a very rough guide but thats the general idea for a safe overclock, id aim for around 400-450 fsb i guess and to not really take that chip over 1.35 volts on air.
you dont mention what cooling your using, a good air cooler is essential, watercooling is also a viable alternative.
sorry I havent ever used an asrock board, as long as you can change the ram dividers, have cpu voltage adjustment and FSB adjustment you should be fine
