With the refresh of the tools we see significant advances in the implementation of the Windows Phone 7 execution model. Developers of WP7 applications should take the time to read about the Execution Model and how it affects your application. This is critically important to ensure your users have the best experience.
A summary of the Execution Model Best Practices.
Yochay’s eloquent blog post explaining the Execution Model.
MSDN overview document for the Execution Model.
These documents currently discuss the execution model as it is implemented for Silverlight applications. Best practices for XNA games will follow, but differ only in elements of implementation.
Please go read – this is important to understand.