First, read and familiarize yourself with the guides here and elsewhere.
Whatever method/guide you use, first start by setting the RAM ratio to the lowest setting. When you OC the CPU, the RAM speed will also increase proportionally. You want to ensure that the RAM is not OCed beyond the manufacturer's specs. and creating instability.
After setting the RAM ratio to the lowest setting, probably 8x, start your OC in the BIOS by gradually increasing the clock speed. This is not an overnight process. After each discrete increase, check for stability and check the temps - idle temps as well as load temps (prime95).
A 30% to 40% OC is feasible using air coolers properly installed.
When you find a stable OC that you are happy with, stop. Quit while you are ahead.