1. Each controller action only calls one model method other than an initial find or new. (Make custom .new or .update methods in the model with all necessary). …
2. Only one or two instance variables are shared between each controller and view. …
3. All model and variable names are both immediately obvious (to a new developer) and as short as possible without using abbreviations. …
4. All custom “finds” accessed from more than one place in the code use named_scope instead of a custom method. …
5. A .find or .find_by_ is never called in a view or view helper. …
6. There is zero custom code that duplicates functionality of a built-in function in rails. …
7. Code has been aggressively DRYed during development. …
8. All functionality used in two or more models has been turned into a library/module. …
9. All logic duplicated between two or more apps has been turned into a gemified plugin. …
10. STI is not used anywhere …
11. Every design choice should yield the most simplistic design possible for the need of users at the current time. No guesses for future functionality were designed into the application. …
12. Close to full test coverage exists at the highest level of the application: on and between controller actions. Coverage is highest for code used by the most number of end users. …
13. All tests pass before code is merged into a shared repository. …
14. Every fixed defect on a deployed product has tests added to prevent regression. …
15. Every plugin installed has been code reviewed. …
Read the entire post at http://www.matthewpaulmoore.com/articles/1276-ruby-on-rails-code-quality-checklist