i dont know about p4's , but you have the right board for it, asus are very good boards for overclocking with.
first thing i would suggest is have a good look at your motherboard manual, as the place to juice up your board is your bios.
if you plan on overclocking there are one or two things you should know first.
1 where the 'reset cmos' jumper is located
if after making changes in your bios your pc wont boot you will need to follow the instructions in the manual to clear the cmos chip and reset your bios back to its default settings (its a good idea to make a note of your settings before you begin as well, or this could lead to problems later).
i dont know if this is your exact board, but i found a link that may be helpfull
P4g8x @ www.ocworkbench.com
P4g8x on ASUS home page (to get the manual)
WARNING: overclock at your own risk as you may cause damage to your hardware and or make your system unstable.