This is just a simple note for me and maybe some other people who'll find this useful on how to install the "smart" bash completion in ArchLinux, which autocompletes arguments, does not complete file names when you hit TAB on a cd command, etc.
It boils down to just two steps:
1. Open a terminal and type:
sudo pacman -S bash-completion

2. Edit your ~/.bashrc (or /etc/bash.bashrc)
Add these lines:
if [ -f /etc/bash_completion ]; then
  . /etc/bash_completion
Then just restart your terminal and enjoy! :)