Here's my top 6 things that probably you should do after installing ubuntu 16.04 xenial xerus. These are general stuff, you may also install software or driver that specific for your system.
1. Run the update command
2. Activate the canonical partners repository
open software & updates, go to tab 'other software', select the 'Canonical Partners' option and then click 'close' button, then choose 'Reload'.
3. Install multimedia codecs, flash player plugin and some fonts
4. Install VLC player (video player)
5. Install clementine (music player)
6. Install google chrome
First you need to download google chrome debian package (.deb) from google chrome official web page. You can install directly after download or you can install through the command line, like this: