Best Practices for Code Organization

Hi folks, i'm relatively new to this area of things although i have been using C# for many years. I have been trying to find a starting point for organizing my code for medium sized projects. What i am after is a relatively detailed example of how a software application solution would be organized in Visual Studio. For example if i worked for company CMP and had an application i wished to create named AppX, no doubt i would start with a solution named: CMP.AppX .. and then begin adding projects. I am aware that every situation would be different and would require different projects and namespaces, but i would like an example of how you guys would go about doing it and some reasons for your choices. eg:

CMP.AppX
   CMP.AppX.Data 
   CMP.AppX.UI   
      CMP.AppX.UI.Desktop
      CMP.AppX.UI.Web
   CMP.AppX.Webservices
   CMP.AppX.UnitTests
   CMP.AppX.Reporting

...and how this would be achieved - what was a project and what was subdir in the project folder etc. Thanks in advance.