The 9 Rules of Object Calisthenics

Calisthenics.md

Object Calisthenics outlines 9 basic rules to apply when performing the exercise:

• One level of indentation per method.
• Don't use the ELSE keyword.
• Wrap all primitives and Strings in classes.
• First class collections.
• One dot per line.
• Don't abbreviate.
• Keep all classes less than 50 lines.
• No classes with more than two instance variables.
• No getters or setters.

Also see the "Your code sucks, let's fix-it" presentation by Rafael Dohms.