Steps

1. Download Ruby .exe installer from http://rubyinstaller.org/downloads. Download railsinstaller at http://railsinstaller.org/ and install it to easy-to-remember path such as C:rubyonrails. This will setup ruby, rails and all other necessary components.
2. As of writing of this post the version of rails bundled on this package is 3.2.13 To get the latest rails 4.0.0 (so you can go through the official getting started tutorial), open a cmd prompt and run gem install rails, then bundle install to install latest dependencies. Make sure you close and reopen cmd prompt once it’s finished.
3. That’s it! Well done rubyinstaller.org for making it so simple

Version Check

Once everything is setup you can check your ruby/rails installation version via command prompt:

c:>ruby -v
ruby 1.9.3p392 (2013-02-22) [i386-mingw32]

c:>rails --version
Rails 4.0.0