You should probably work your way through the thread:
it covers all of the basics from HelloWorld to more sophisticated issues such as event handling and cross Apartment communication with a number of code samples. You can also learn a lot from taking apart other plugins and experimenting.
While the thread is a bit old, it's still totally relevant, especially since the API hasn't changed in years (the last update was in November 2014) and according to SSG is not likely to ever get updated again. It was implemented as a volunteer "pet" project of a couple of Turbine devs, none of whom still work for SSG and SSG doesn't have the resources or the inclination to research the existing implementation in order to enhance it.