There used to be lots of great guides around, including one on Toms, but a lot seem to be removed now. Searching on google I came up with these:
http://www.overclock.net/intel-cpus/289573-my-experience-overclocking-q6600-basic-guide.html
http://gameandtechreviews.wordpress.com/2007/12/12/q6600-g0-stepping-overclock-guide/
http://www.clunk.org.uk/forums/overclocking/1-c2d-overclocking-guide-beginners.html
I have my Q6600 G0 (refers to the stepping, G0 is easier to OC than the standard B3) overclocked to 3.2 ghz on air. I could have gone to 3.4 but was happy with that and can still play pretty much any game with it some 3 years later (depending on the gpu of course!). You'll need a new cpu cooler (you shouldn't do OC on a stock cooler) and probably good ventilation or airflow in your case.
As the second link says, you should download some programs to check settings, temps and stability tests. The ones it mentioned are what I used oh so long ago (cpu-z, coretemp, prime95). Remember, you are looking for your highest stable overclock. So please don't leave your cpu on 3.2 if it causes stability tests to fail or your cpu temperatures hit 90C under load
The third link has good info on the BIOS settings for the P5K and P5B Deluxe boards so they should be similar to what you have.
It's going to be very hard to find exact voltages, etc as that varies by motherboard, power supply and cpu stepping. I went with 8 x 400, leaving the FSB
RAM ratio on 1:1, to keep things simple. I later tried OC'ing my RAM but couldn't get it stable and gave up. For your reference, here are my OC voltage settings according to my BIOS on an Asus P5E motherboard but yours will very probably be different:
Vcore = 1.25625
DRAM = 2.04 (for DDR2 400MHz. It was rated at 1.8v but has a 2.1v setting.)
NB = 1.29