Custom controls

Hi friends,i am new to xamarin.forms ,i know cross platform is to handle 3 apps (Android,IOS,Windows phone) with a shared library ,but i want to know which design method i should use to develop xamarin.forms (XAML) or (.CS) ,because i need to include customized controls like image-button,radio button,Camera API.

1.which design method i should follow To use these customized controls ?
2.If Xaml ,How to do design for Customized control?
3.If (.cs) any samples available rather than this (http://developer.xamarin.com/samples/UsingCustomRenderers/)

Thanks in advance.