1. Install fish via Brew
2. Optionally install Oh My Fish!
3. Add fish to known shells
4. Set default shell to fish

brew install fish  
curl -L https://github.com/bpinto/oh-my-fish/raw/master/tools/install.fish | fish
sudo echo /usr/local/bin/fish >> /etc/shells
chsh -s /usr/local/bin/fish

Add any the following functions to ~/.config/fish/config.fish

Repeat previous command with administrator rights

function sudo
    if test "$argv" = !!
        eval command sudo $history[1]
    else
        command sudo $argv
    end
end

How often did you type cd.. instead of cd ..?

function cd..
    cd ..
end

Simplify the creation and deletion of Git tags

function tag
	if test $argv[1] = "-d"
		# delete tag if provided
		if test $argv[2]
			eval command git tag -d $argv[2]
			command git push origin :refs/tags/$argv[2]
		end
	else
		# create new tag and push
    	eval command git tag -a $argv[1] -m $argv[1]
    	command git push --tags
    end
end