Mark Thompson, at Prototron Circuits, wrote a terrific article about strategies to improve your success when working with a quick turn prototype shop. Much of what Mark has to say makes sense here at Sunstone Circuits as well. PCB Design 007 Article
Another source for "best practices" when working with your PCB solutions provider. Remember, though, Sunstone has 24/7/365 customer support, live, to help walk you through these best practices BEFORE you submit your quote or order.