application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery
  
  before_filter :set_counter
  helper_method :counter
  
  protected
  
    def counter
      @counter
    end
  
    def set_counter
      @counter = Counter.new
    end

end

counter.rb

class Counter
  
  def initialize(i = 1)
    @i = i
  end
  
  def current
    @i
  end
  
  def increment!(by = 1)
    @i += by
  end
  
end

index.html.haml

%h3= "#{counter.current}. Something"
%p Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

%h3= "#{counter.increment!}. Something Else"
%p Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

%h3= "#{counter.increment!}. Other Stuff"
%p Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.

This is handy in cases when you need to manually set numbering in a view. The example (index.html.haml) is not a good one given you would obviously use an ordered list with that content...but you get the point.