Step 0:  Install Vim with ruby and python support.  
You can check if your install has these settings by looking at the output of 
vim --version
You should see +ruby +python.  If you do not see both of these options then I suggest installing Macvim or building Vim from source with the flags indicated in the Vim installation instructions.

Step 1: Clone this repo to .vim and symlink .vim/vimrc to ~/.vimrc 
cd ~
git clone git://github.com/mrmargolis/vim_files.git .vim
ln -s ~/.vim/vimrc ~/.vimrc

Step 2: To get all the plugins setup
cd ~/.vim
git submodule init
git submodule update
rm -rf ~/.vim/bundle/snipmate.vim/snippets        
cd ~/.vim/bundle/command-t/ruby/command-t
ruby extconf.rb
make