There are tips to be found on the internet. Some say that recompressing the XAP file with something like WinRAR on its "best" compression setting will help. But that was in the Visual Studio 2008 / Silverlight 2 days. Now if you're building a Silverlight 4 app in Visual Studio 2010 it's already going to be compressed about as heavily as it can be. So I'm going to talk about other effective techniques that will help you today.