Next stop should be a guide for your particular motherboard. Google is your friend.
Go through the guides. Then take your core voltage off Auto and set your memory voltage to factory recommended values. Change the System Memory Multiplier (or whatever your BIOS calls it) from AUTO to 2.00, 2.00B, or 2.00D - whichever you need to set the Memory Frequency to twice 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 533 MHz.
Download CPU-Z to check your FSB:RAM ratio. It should be a 1:1 ratio.
The guides will tell you how to test for stability. Keep the core voltage under 1.5 volts and the loaded core temps under 70 C .
Ok. I've just set my ram speed to from 1:1.20 to 1:1. (still on e6750 - i'm gonna get q6600 in a few days) So that's the principle - to set FSB:RAM to 1:1, make sure to set my FSB to the one that my ram can work on and then the lowest, stable running voltage on CPU ?
You can tweak the cpu voltage down or up as needed (lower than 1.5). With the ram voltage, just set them to your manufacturers specification, and forget about it unless you run into stability issues at your rated speed, then a small bump up should be ok.
As JSC said, there is a guide with good info on how to overclock. I haven't read it, but I'm sure they talk about the different voltages, and how to test for stability.
I know on my Q6600 I got to 3.2 without upping the voltage. I got 3.0 and could actually lower the voltage just a little to save a little energy. You may want to see how high you can go without that and see if it is acceptable.
I have an IP-35 Pro (essentially the same motherboard) and a Tuniq tower. It has been running like this for 3 years or so with no issues.
Also, consider dumping that single stick of ram (or getting some matched memory for the others) to get the benefits of dual channel memory. It probably won't make much difference, but it is something to play with.