How To Install Ruby on Rails on Mavericks (OSX 10.9)

xcode-select --install

ruby -e "$(curl -fsSL https://raw.github.com/mxcl/homebrew/go/install)"
brew doctor
brew update

brew install rbenv ruby-build openssl
echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
source ~/.bash_profile

Installing Ruby 2.0.0 on OSX 10.8 Mountain Lion

ruby <(curl -fsSkL raw.github.com/mxcl/homebrew/go)
brew doctor
brew update
brew install apple-gcc42

brew install rbenv ruby-build openssl
echo 'eval "$(rbenv init -)"' >> ~/.bash_profile
source ~/.bash_profile

rbenv install 2.0.0-p0
rbenv rehash
rbenv global 2.0.0-p0
rbenv shell 2.0.0-p0