I'm not sure if the guide Shadow703793 suggests this but what I tend to do is:
1) Find my RAM's max overclock by setting motherboard ratio to something crazy (2:5 if possible), lowering the CPU multiplier, and bringing up the FSB until Memtest starts complaining.
2) Drop back the RAM to a low speed and loose timings, and start to find the max FSB overclock, keeping the CPU multiplier low.
3) Bring up the multiplier until you get close to where you want to be while remaining stable
4) Adjust the multiplier, FSB, and RAM clocks until you hit a 1:1 ratio and are roughly where you want to be.
Example: I found that my CPU can hit 3321 MHz (368x9), my RAM can hit 1249 MHz, and northbridge starts complaining at ~1700 MHz. After a while I tried tightening up the timings on the RAM, and could only get to about 900 MHz at CL4. So... a bit of math later and I ended up at:
CPU @ 3.2 GHz (400x8, 1600 MHz FSB), RAM @ 800 MHz CL4 (1:1 ratio)
After that it was just a case of finding out how low I could bring voltages before I started bluescreening...
Whole process took about 2 weeks (mainly because I wanted to make sure the system was stable after 24 hours of Prime95, and could go through a full run of Memtest, including the 2 optional tests)