10 Steps to Ruby 2.x and Rails 4.x on Mountain Lion

1) Download and install Xcode Command Line Tools
Mountain Lion file name: xcode462_cltools_10_86938259a.dmg

2) Install GitHub for Mac
This also has an option to install the Git command-line tools. Choose that option.

3) Install RVM
$ curl -L https://get.rvm.io | bash -s stable –ruby

4) Source rvm to open in the existing shell
$ source ~/.rvm/scripts/rvm

5) Set default Ruby version
$ rvm –default use 2.1.0

6) Update Gem manager
$ gem update –system

7) Use the global Gemset by default
$ rvm gemset use global

8) Update all Gems
$ gem update

9) Don’t download Gem documentation at install
$ echo “gem: –no-document” >> ~/.gemrc

10) Install Rails
$ gem install rails