1. Install fish
2. Run git clone https://github.com/dorentus/.fish.git ~/.config/fish
3. Run fish and have fun
4. Optionally, set fish as login shell if you wish

If you're using fish as login shell and using vim, remember to add set shell=/bin/sh to the top of your .vimrc file. Reference: http://stackoverflow.com/a/12231417/90172