Asus P5NE-SLI Motherboard With an E6750 Core 2 Duo Cpu (Want to Overclock!)

Hi People I have been Given today An Asus P5NE-SLI Motherboard With A E6750 Cpu, 2 GB DDR2 PC2-5300u Single Sided Crucial RAM, 1 GB DDR3 Nvidia Geforce 210 Gpu. I Have Attached a Zalman Cpu Heatsink/Fan to the Processor, The Gpu is Already Cooled with its own Fan and I have Modded the North and Southbridge with Air Cooling also. She Has a 500W Power Supply So in My head I am good to go and Start Overclocking this Badboy!!! Anyone got any Advice on How to go Around this?

Many Thanks
Nathan Milnthorpe