GIGABYTE's own Taiwanese technical marketing dude, Hicookie, has created a very in-depth guide which explains how to overclock an Intel Core i7 920 processor all the way up to 4GHz.
Since it is GIGABYTE marketing material, naturally a GA-X58 Extreme motherboard is used. It starts by telling you which parts you need, how to setup and prepare the system for overclocking and much more.
If you are new to Core i7 overclocking, and let's face it, pretty much all of us are still, it is well worth the read.
You can grab the guide here (PDF).