See the documentation in the Business Object Server topic document (in the Learning Resources); there is also a code sample under the Business Object Persistence folder in the Learning Resources.
The RSMs can be called synchronously or asynchronously. The code sample cited uses an asynchronous call. It's a Silverlight sample, but you should be able to inspect the code and transplant the RSM call and callback to a WPF or WinForms app.
(Note for future reference: I've just moved the Remote Service Methods code sample to the Business Object Server folder for future release of DevForce.)