Component capabilities
Bear in mind that if you have a processor capable of a 50-percent or more speed increase, it's unlikely that your video card or memory will enjoy running that much faster. A motherboard that can be overclocked will either provide multiple PCI/AGP and memory bus ratios or allow you to lock them at their preferred operating parameters. Memory speed
Memory speed is often tied to the FSB, but there are boards that will lock the memory bus speed. Don't do it if you don't have to. Half the performance increase you may see from overclocking a CPU comes from increasing the speed at which the processor can talk to the memory. High-speed memory abounds in the market for DDR systems, which constitute the majority of computers out there. This is especially true in the case of the Celeron, since a sizeable portion of what makes it a "value" processor is the reduced memory speeds. Power needs
You'll need to know how much power your processor uses. Just like a motor running at a higher speed, you'll need to give your CPU more power. This is one of the "risky" aspects of overclocking. Use too much power and you could burn out your processor. A mere shift in the manufacturing process can change the operating voltage of a CPU by a significant amount, so I don't recommend running a processor at a voltage more than 10 percent above what is listed for your type of processor at the new speed. Even then, you're relying on the engineering design overhead, which is not something for the faint of heart. Individuals bent on squeezing out every last iota of performance can boost the voltage, but those who prefer long-term stability should only do so for testing. This is also the best time to check the power supply in the system you intend to overclock. Speed requires power, and unstable power inevitably leads to unstable processors. Intel processors are hungry beasts, consuming 40 to 75 watts of power. Your graphics card may take another 50 watts of power. You're consuming 100+ watts of power right there -- between half and a third of a typical OEM unit. Multiple or fast drives will take still more power, as will USB and FireWire devices, especially hungry bus-powered ones like scanners or hard drives. I recommend a 350-watt power supply at a minimum in any computer you intend to overclock, and more if you have several SCSI drives or a RAID array. Cooling and airflow
One of the most important things you'll need is something too often neglected: a potent cooling solution. Overclocking causes circuits to cycle faster, generating more heat. Insufficient cooling can cause permanent heat damage to your processor. Surprisingly, the heat sink and fan unit that Intel ships with its processors is a fairly durable component. However, if you have trouble with stability, consider upgrading to an "enthusiast" unit. Combined with a good silver heat transfer medium, it will keep your system much cooler. In addition, don't neglect the airflow in your case. Your processor is still at risk if heat can't escape the case. For overclocking, don't rely on the power supply's exhaust fan to handle your cooling needs. At the very least, you should have an exhaust fan at the top of the case in addition to the one in your power supply. Adding a second fan at the bottom of the case to draw air in greatly improves the airflow and only costs a few dollars. Be sure that the cooling solution you choose is specifically designed for your processor. Improperly mounting a heat sink, or using the wrong model, can physically damage your processor. The sites below are excellent resources for determining the optimum heat sink/fan combinations for Intel's Celeron and P4 chips:

• Intel Celeron Specifications
• Intel Pentium 4 Specifications