If there are some methods you wish all of your Active Record instances would have, the easiest way to add them is to monkey patch. Here is how to add a random method that retrieves a random record from a table:

module ActiveRecordBaseExtension
  def random
    self.find :first, 
              :offset => (self.count * rand).to_i
  end
end
ActiveRecord::Base.extend ActiveRecordBaseExtension

This code can be appended to lib/rails_extension.rb which should be required in the config/environment.rb file:

require 'lib/rails_extension.rb'