god.rb

class User < ActiveRecord::Base
  attr_accessible :email, :first_name, :last_name, :username

  before_validation :lol, :on => :create
  before_validation :yay, :on => :create
  before_validation :yay, :on => :update

  def lol
    puts "Running lol"
  end

  def yay
    puts "Running yay"
  end
end

a = User.new()
a.save!

...
only prints
Running lol