Overclocking is not an exact thing. Depending on your components, your overclocking results can vary. The best, and safest, method is to overclock ONE aspect at a time by a small amount. Then test it, for stability and safe temperatures. If it works, overclock a bit more. Then repeat the process. Eventually you'll find the limit, the point where it's no longer stable. Then you can move on to another part of the overclocking.
What you want to avoid is hearing someone say "I raised my base clock 100mhz" and you go and raise yours 100mhz all at once.