Barry Gordon from the CommandFusion Software Google Group has written up a great guide to the basics of Serial Communications.
The guide was originally written for the Pronto PRO, but Barry is in the process of adding CommandFusion relevant information.
The document "Serial Communications 101" can be found here.
Thank you to Barry Gordon for providing this information and allowing us to share it. Here is the link to Barry's full web site where a lot of things related to Home Theaters and Home Automation are located http://www.the-gordons.net/