Windows Communication Foundation (WCF) is a great tool for building client/server applications in the .Net environment. It is one of those technologies that can be challenging to dig into when services are just one of many tools needed to assemble a business application, as opposed to being an end in itself. With some of my co-workers in mind, here are some of the lessons I have learned in using WCF for internal, line-of-business, applications. These notes, which will be published in several parts, assume a basic understanding of WCF and contracts.