Ruby on Rails Code Quality Checklist

# Each controller action only calls one model method other than an initial find or new.
# All model and variable names are both immediately obvious (to a new developer) and as short as possible without using abbreviations. …
# All custom “finds” accessed from more than one place in the code use named_scope instead of a custom method. …
# All functionality used in two or more models has been turned into a library/module. …
# All logic duplicated between two or more apps has been turned into a gemified plugin. …
# Every design choice should yield the most simplistic design possible for the need of users at the current time.
# Close to full test coverage exists at the highest level of the application: on and between controller actions.
# All tests pass before code is merged into a shared repository. …
# Every fixed defect on a deployed product has tests added to prevent regression. …
(Link: Ruby on Rails Code Quality Checklist)