Defining methods in an included module inside your class allows modification by modules later.

module_overrides.rb

class Dog
  module InstanceMethods
    def bark
      "Arf arf!"
    end
  end
  include InstanceMethods
end

dog = Dog.new
dog.bark
#=> "Arf arf!"

module JapaneseBark
  def bark
    "Won won!"
  end
end

Dog.send :include, JapaneseBark
dog = Dog.new
dog.bark
#=> "Won won!"

# This is versus:

class Cat
  def meow
    "Mew!"
  end
end

cat = Cat.new
cat.meow
#=> 'Mew!'

module JapaneseMeow
  def meow
    'Nya!'
  end
end

Cat.send :include, JapaneseMeow
cat = Cat.new
cat.meow
#=> 'Mew!'