Hello. I was in your spot just a few weeks ago. I wanted to overclock this beast and I never have before. Well I will tell you what I did!
As many will tell you, you can only go +135mhz on the GPU core without messing with bios, voiding warranties, etc. So if you wan't some extra performance, and to safely overclock, I will tell you how I did it. I downloaded Asus GPU Tweak. I searched downloads at asus.com and downloaded it directly from their site. I found it perfectly safe to max the core (from 950 mhz to 1085 mhz) and I increased the mem clock from 5000 mhz to 5500 mhz. (This is how it appears in Asus GPU Tweak, but it is actually 2500 mhz to 2750 mhz). Either way. I used Asus GPU tweak because not only is it made by asus, it is really easy to use. If you check it out you will see. Don't go maxing out the mem clock, it will let you go up A LOT. Your screen will just go black, trust me! Just max the core, and increase mem clock from 5000 to 5500. Here are my results.
Stock
Overclocked +135/+500
As far as overclocking the CPU and RAM, not my department. I just wanted some extra performance out of the GPU. The CPU already boost's itself to 3.4 GHZ in mine, so not messing with that. As far as memory, sounds like a nightmare to mess with.