The G31/G41 chipset is an economy, entry level chipset. Unless you get really lucky, you will not be able to push the FSB freq past about 360 MHz. I have a G'byte G41 board. FSB freq of 352 MHz works. 353 MHz doesn't. So the motherboard may be the limiting factor.
Most of the overclocking guides are guides, not cookbooks. There are no step by step instructions.
I am unfamiliar with the Asus BIOS (I use Gigabyte motherboards), so you will need to do some experimentation.
Go through the guide. Then take your core voltage off Auto and set your memory voltage to 1.65 volts. Change the System Memory Multiplier (or whatever your BIOS calls it) from AUTO to 4.0 - whichever you need to set the memory clock to 4 X the FSB. Then when you increase the FSB, the memory clock will rise in in proportion with it. At an FSB of 266 MHz, your memory clock should be at 1066 MHz.
Your goal is a 1:1 FSB:RAM ratio.
Once you get that, you can jump straight to a 300 MHz FSB (3.45 GHz). You will probably need to increase CPU core voltage a little. Use Prime95 to test for stability.
Next, you can jump to 333 MHz (about 3.8 GHz.) Repeat with the adjustments and testing. Unless you get a "bad" chip, an E6600 Wolfdale should be able to run this high.
At this point, you are at the limits of your memory, but you may be able to push a little higher.
Keep the core voltage under 1.45 volts and the load temps under 70 C.