gistfile1.rb

module MyConcern
  def shared_method
    #do something with method_specific_to_class
  end
  def method_specific_to_class
    raise NotImplementedError.new
  end
end

class MyClass
  include MyConcern
  include InstanceMethods
end

module MyClass::InstanceMethods
  def method_specific_to_class
    #override concerns method
  end
end
end