# Proposed benefits:
# * more verbose, but you can see more clearly all the "stuff" your method is using
# * easier to re-use methods, since they're not coupled to instance var names

class UsersController < ApplicationController
  def update
    load_user
    check_if_user_now_active
  end

  private
  def load_user
    @user = User.find(params[:user_id])
  end

  def check_if_user_now_active
    flash.add(:info, "active") if @user.active?
  end
end

vs

class UsersController < ApplicationController
  def update
    @user = load_user
    check_if_user_now_active(@user, flash)
  end

  private
  def load_user(params)
    User.find(params[:user_id])
  end

  def check_if_user_now_active(user, flash)
    flash.add(:info, "active") if user.active?
  end
end