Make sure your RAM:FSB mhz ratio is 1:1 then slowly start taking your FSB up in increments.
It's important to get high quality RAM when overclocking. RAM that's been clocked higher than the stock speed of your CPU's FSB and warranted at around 2.1 or 2.2 volts (so you know it can take overclocking without getting fried).
So in my case... I have an E6600. The stock FSB is 266 * 9 which gives me 2.4ghz clock speed. My RAM has been rated at 400mhz, so, if all goes well, I can take my FSB up to 400 * 9 which gives 3.6ghz.
Keep in mind to do high overclocks like that, you will need to tamper with the voltages running both to the ram and the CPU. In other cases you may even need to change voltages running to the pciE slots, the northbridge etc. shit like that.
Should always do it from the BIOS. Best way to be safe is just go up incrementally and always test a new configuration using benchmark applications and stress testing tools.