On the Symfony blog today they've officially announced the Symfony Best Practices initiative that's being ramped up to help provide a solid resource for Symfony developers and guide them towards more correct development within the framework (and its components).
Since the publication of Symfony 2.0, the Symfony Community has created an unofficial set of recommendations for developing Symfony2 applications. Unfortunately, a lot of these recommendations are in fact wrong. They unnecessarily overcomplicate things and don't follow the original pragmatic philosophy of Symfony.
This guide, soon to be published at http://symfony.com/best-practices will share 31 of the best practices gathered by Fabien Potencier, Ryan Weaver and Javier Eguiluz from their own experience and the practices the community has found along the way. The things in this guide will be optional, not required, to make Symfony-based applications work, so don't worry if you're not following them exactly.