This page presumes you have gone through the Getting Started page and have successfully installed Xamarin Studio, Xcode, and all the requisite libraries. If you're ready, let's get the HelloRhino app building on both iOS and Android, and after we can take a look at how all the pieces fit together to share code between the platforms.
Mac OS X Step-by-Step Instructions
Tip: Xamarin Studio's trial edition places a 24-hour time limit on app builds. You may get this message that says “Trial executable has expired (24 hour limit)” error dialog. This is an annoyance. To work around this pesky limitation and continue to tinker during you 30-day trial, you need to do the following: Double-click the name of the project you are trying to build in the Solution Pane of Xamarin Studio. This should bring up the Project Options dialog. Under the Build section on the left, select iOS Applications. Change the Bundle Identifier to something else, such as: com.yourdomain.foobar. Click OK. In Xamarin Studio, select Build > Clean All. Finally, reset the simulator.
Windows 8 Step-by-Step Instructions
WARNING: This section is a work-in-progress: Information may be missing or incomplete.