overclocking is a hobby of passion and requires either a fools luck or a saints patience to be good at.
My personal suggestion is to read read read and read some more. there simply are no easy 1,2,3 steps to overclocking well.
In essence, overclocking is just making a piece of hardware work faster so anything that can be set manually for that piece of hardware can potentially be set differently to cause it to operate at a higher rate. with CPUs this would typically be the FSB and/or voltage. but if you put the voltage up for something, heat becomes an issue so most overclockers employ custom 3rd party cooling solutions.
but CPUs are not the only thing that can be overclocked.
Try reading some how to guides off sites like XtremeSystems.org and OCUK. then start reading discussion threads in detail and listening to what other guys are doing with their systems. this will give you the most up to date info and hopefully make some decisions for you.
good luck and happy clocking
-D-nosey aren't ya, readin me sig?