Good Application Development Practices

• The core components of the application must be identified early and a significant amount of time and effort must be devoted to their design, development and testing. A perfect example of a core component is the Subscription functionality.
• If possible, the smartest people must be assigned to these tasks.
• Logging must be enforced in all important areas of the application. This ensures that we have enough diagnostic information to troubleshoot potential issues in production. Logging is also necessary to troubleshoot issues where the application might not be blowing up, but is not performing as intended.
• The first page in the application that the user lands, after login, must not contain any time-consuming calls that can lead to page timeouts. This will prevent the user from logging into the application and accessing any other areas of the application.
• Avoid Single Point of Failures. e.g. Do not use a single large object to share data across the whole application. e.g a cache object that stores a huge amount of data that might not be required by all areas of the application. Serialization and deserialization of a large object is a costly process and can slow down the entire application and may even bring the whole application to a halt.  
• There should be a single point of access to all common objects used across the application. This ensures that the application behaves consistently. e.g. When trying to extract the one and only element from a common list, one part of the code must not call SingleOrDefault while another calls FirstOrDefault.
• Be extremely cautious if your application uses a memory cache to store objects. When returning values from the cache, always return a deep copy of the object and not a shallow copy. This ensures that the calling code gets it's own copy of the cached data including all reference types. More importantly, this ensures that the calling code does not tamper with the original object in cache.
• If  the application utilizes separate Read and Write databases, ensure that the database objects(e.g stored procedures) in either case return consistent results.