If It Ain't Broke.....

.....tweak it!

There's never a reason to overclock, if everything already works as fast or as well as you need. On the other hand, there's no such thing as too fast. Not in computing, anyway ;)

There are lots of ways to overclock, but I have found, (using a BIOS that allows it) increasing voltage on both processor & RAM, with an increase of clock speed applied to the processor, gives good results. Today, I did just that. I upped the cpu voltage from 1.4v to 1.5v, the RAM by +0.2v & increased the cpu clock speed from 200 to 210. This raised the processor's speed from 3.2Ghz to 3.36Ghz. My new benchmark best is, as of today, 43,455.
If you're new to overclocking, I strongly suggest only small increments, as hardware can be damaged if you apply too much. Also, use components specifically designed for overclocking. One company who makes these, is OCZ.

Benchmarking is not the only test for overclocking, but provides a tangible score for comparisons.
By far, the best test of overclocking is using your PC as you normally would. If there is a noticeable, positive difference in performance &, after a lengthy period of time (24-72 hours) it is still stable*, then it has worked.

* Stability means no blue screens, or difficulty booting up.
Check to see that your system is still being cooled efficiently by: 1. Put your hand near your power supply, at the back of your case & feel the air blowing out. (It should be warm, but not hot.) or 2. Monitor temperature levels in BIOS/CMOS (if you don't already have a desktop program for that).
Another sign of instability can be programs failing to load as expected, or images appearing fractured/pixelated.

Overclocking is dangerous, particularly if you're new to it, but can be rewarding if you've reached the very limit of upgrades that you can afford, or are available.