ive overclocked my cpu and my video card... as far as overclocking goes for the cpu make sure you have a very good cooling system.. also dont do huge overclocks at once... take baby steps... some over clocks you have to increase the voltage of the cpu in order to maintain your clock without it freezing up on you... i use a program called prime 95 to do cpu stress tests ... you have to do stress tests and pretty much force the cpu to overheat just to see what your limits are... i have a socket 939 amd64 3700+ runs at 2.2 has a 1mb lvl 2 cache... ive gotten a 600mhz overclock from it running at 2.8 thats a 25% OC... i used a zalman cooler... I used a DFI LAN Party Ultra-D UT NF4 Motherboard. prime95 stress tested for 24 hours no errors... i had to increase my voltage by 4%... also the more you increase the voltage... the greater you cpu will run hotter... also depending on the system you are overclocking... by bumping up the FSB of the board you increase the speed (Mhz) of the RAM. MOST RAM CAN NOT HANDLE OVERCLOCKING!!! to keep the ram the same frequency when you bump up the front side bus, you must decrease the speed of the ram. but by bumping your RAM down and bring the FSB up it brings the speed of the RAM up finding the perfect OC (overclock) of the FSB to suite your RAM take time and many test trials... also overclocking decreases the life of the processor... and is not really recommended by novice users or users that are POOR like i am... as far as video cards go... pretty much the same thing... except you can find programs that will increase the speed of your GPU... and now most day motherboards are out that use software overclocking rather than using bios overclocking... any questions?
now i dont know EVERYTHING about overclocking but that is just my experience using my equipment