1) Install latest XCode
2) Install the "Command Line Tools for Xcode"
3) ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go)"
4) brew install autoconf automake libtool pkg-config openssl readline libyaml sqlite libxml2 libxslt libksba
5) brew install https://raw.github.com/Homebrew/homebrew-dupes/master/apple-gcc42.rb
6) curl -L https://get.rvm.io | bash -s stable
7) source /Users/you_user/.rvm/scripts/rvm
8) rvm pkg install openssl
9) rvm pkg install yaml
10) rvm install ruby