Standard of Code Sequence of model

 class Model < ActiveRecord::Base

   #all mixins

   include Something

   extend Something

   #other stuff

   acts_as_taggable

   paginates

   #associations

   has_many :something

   belongs_to :something_else

   #validations

   validate_presence_of :something

   #scopes

   scope :something

   #instance methods

   def instance_method

   end

   #class methods

   def self.method

   end

   #private methods

   private

   def method2

   end

End