If you follow these instructions, you will probably be looking at an expensive driver, but it will be worth it. Look diligently for the driver you want at the lowest possible price. Check several stores, such as Dick's Sporting Goods, the Sports Authority or your local pro shop, and online at sites like the Golf Warehouse.
Don't buy the first one that you think may be right for you; buying a driver isn't a form of love at first sight. Take your time, and the right driver will find you.