Mountain Lion Setup with Xcode, RVM, and Homebrew

If you don't check this page out first, you're going to have a bad time: http://www.moncefbelyamani.com/how-to-install-xcode-homebrew-git-rvm-ruby-on-mac/

This is an excellent post and one that I have followed every time (with great success). I have followed this guide four times: laptop, desktop, and two Bamboo build agents.

Major props to the author for an excellent post.