The overclocking capability of any component depends on the component itself. Some are extremely overclockable, others can be moderately overclocked, and others just can't be overclocked at all.
With that said, most components can be overclocked to some degree or other (although it does depend on whether your system (BIOS and individual Drivers
) give you overclocking access).
Assuming that you are able to overclock, you need to take it slowly and methodically, remembering to test at every stage watching for any sign of system instability (in which case, you have gone too far and need to back off the settings to the previous stable ones).