I am now a slave to contract first development when it comes to service oriented development.  When designing service oriented systems think about creating your contracts first (typically WSDL for web services).  Today this is more difficult than it should be, due to the fact the tools to do this are behind; however Visual Studio 2005 and Orcas will help.  Take a look at the whitehorse features to get started.  More information on white horse can be found here (http://msdn.microsoft.com/msdnmag/issues/04/07/whitehorse/)

Aaron Skonnard from Pluralsight has a great blog entry on contract first.  http://pluralsight.com/blogs/aaron/archive/2004/08/27/2092.aspx

Happy coding!

Ed Ferron