Madshrimps have posted a short over-clocking guide for the X1900 series of cards. The article goes over the different software tools, cooling, basic and advanced over-clocking options. The guide should be useful for anyone starting out in over-clocking.
You currently own an x1900 series video card but you are now itching to compete and get the maximum out of your card. Some would wonder at this fact simply because this is arguably the fastest GPU available (when this guide was written). But we all want the most out of our investments and this is one way of doing it. But it does come with a risk.