Code exchange between MonoTouch and MonoForAndroid

What would be the best practice for exchanging the logic of C # logical operations between MonoTouch and Mono for Android projects?

Edited: My original question was about physical file sharing:

• What do you propose to use: network file sharing or some kind of version control code (git, svn)? In my case, I use two workstations - Mac (MonoDevelop with MonoTouch) and PC (Visual Studio with MonoDroid).
• What about the folder structure of Solution / Project? In “Blog Post: Xamarin Mobile World Congress 2012 Unofficial Conference App Released! ” The sample structure is rather confusing: several solutions in one folder, and then different platform projects in one subfolder with different folder and project names. This cannot be performed nativly with an IDE. Do they edit the contents of decision files and folder names manually outside of the IDE?
• And for projects with a common code, which profile (template) to use? Monotouch has a few: Empty Project, MonoTouch Library Project Projects and MonoTouch? In Android, I supose - Android Class Library?