I can't play a DVD on my Ubuntu laptop. I've tried VLC. A window with a traffic cone opens and the Drive spins for a short time, then stops. Nothing else happens.
It's usually easier to just install the restricted extras package:
$ sudo apt-get install ubuntu-restricted-extras
If you have any problems the official Ubuntu documentation on playing DVDs has a good troubleshooting guide as well.
The specific steps outlined in @illuminE's answer are from this page as well, mainly:
$ sudo apt-get install libdvdread4 $ sudo /usr/share/doc/libdvdread4/install-css.sh
Make sure you have the proper codecs and libraries, including libdbdcss2:
sudo apt-get install libdvdread4