The Patterns & Practices group has released a Codeplex project on SharePoint development best practices and guidance. This is a very comprehensive guide and will eventually be released to MSDN. The team is asking for feedback and has released it on Codeplex to faciliate collaboration within the community. I encourage you to review the information included in the guide and provide feedback if you see fit. Thanks to the Patterns & Practices team for their excellent work. App dev on SharePoint is a challenge and it is very helpful to have all of the lessons learned compiled into a robust set of documentation.