Some setup you must do manually if you haven’t yet:

1. Ensure you have defined default url options in your environments files. Here 
   is an example of default_url_options appropriate for a development environment 
   in config/environments/development.rb:

     config.action_mailer.default_url_options = { :host => 'localhost:3000' }

   In production, :host should be set to the actual host of your application.

2. Ensure you have defined root_url to *something* in your config/routes.rb.
   For example:

     root :to => "home#index"

3. Ensure you have flash messages in app/views/layouts/application.html.erb.
   For example:

     <p class="notice"><%= notice %></p>
     <p class="alert"><%= alert %></p>

4. If you are deploying Rails 3.1 on Heroku, you may want to set:

     config.assets.initialize_on_precompile = false

   On config/application.rb forcing your application to not access the DB
   or load models when precompiling your assets.