Depending on the capabilities of the motherboard, specifying the parameters settings that define CPU overclocked modes can be done either by using BIOS Setup or by setting the motherboard jumpers. Evaluation of the overall system performance and stability can be done using specialized tools, which usually include test programs.
There are two ways of changing the system parameters. The first one is to use the appropriate settings in BIOS Setup. Most current motherboards that provide built-in overclocking capabilities, such as SoftMenu from Abit, allow the bus frequency and various voltages to be measured directly in BIOS Setup. All such capabilities are described in the documentation supplied with the motherboard. However, many motherboards only allow parameters to be measured using jumpers and switches located on the motherboard itself.
It is first necessary to figure out which method of overclocking is provided by the motherboard. Then, you'll have to carefully read the documentation on your motherboard, especially the sections that describe overclocking capabilities and methods.