The first thing you should look into is flashing the card so it's overclockable. The 9700 non-pro is clock locked. http://www.3dchipset.com/bios/index.php

The stock HSF is pretty decent already, but it isn't making good contact with the core. (there's a metal shim around the VPU that keeps the heatsink from pressing against the core firmly.) I recommend removing the shim. If you want to use something more robust than just the stock HS, find something made of copper.. otherwise scrape off the thermal interface material (the soft plastic like yellow stuff) and reattach it w/some Arctic Silver.

Once you've made all the modifications to your card, the actual ocing is pretty straightforward. Use a program like Powerstrip or rage3d tweak to change the clock speeds.

EDIT: good grammer is good.