I got started by going to XAML and Code Behind tabs on ESRI's sample pages and copy/pasting right into my project. At that point, you don't have to change a thing. Just push F5 and you get a web page that does what the sample does. From there, you can change what the map is pointing to and other things until you get it the way you want. Then go to the next sample.
Of all the API's I've tried Silverlight is the easiest to figure out in my opinion. I wish all of their API samples were done just like the Silverlight samples.
Good Luck