I recommend to start a .NET App with WCF. Get related to WCF, its advantages a as to expose a service endpoint with multiple binding as http, tcp, etc, so you are able to SOA your App.
I use the UML Robustness Analysis to discover the functionality that will be exposed as services.
I think that there is not silver bullet code for SOA, SOA is about design, organization of the system methods in order to expose services that orchestrates the handling of the responsibilities of application entities.
For example, to look for a flight booking, your SOA service have to expose a contract, with all necessary data to handle the service request. It will return all necesary data for the next service, book flight.
There is an excelent article about SOA in the Architecture Journal #21 -Service Orientation Today and Tomorrow Article An Enterprise Architecture Strategy for SOA written by Hatay Tuna.
SOA is about logic exposure, design, logic ecapsulation, is not about code, the code supports the orientation.