Successful design of modern, complex mixed-technology printed circuit boards is an ever-evolving task. As technologies change, techniques employed by designers must evolve accordingly. The aim of this guideline is to ensure that designs are done as correctly as possible on the first attempt. Doing so has been repeatedly found to yield good results from simulations and testing, with minimal design modification required. Regardless of the mathematics and simulations that may be employed, strict adherence to best practices is most likely to make the board “just work”.