Hi Daniel,

The easiest way is to use an automated install script! I use them all the time and they work like a charm. First create a new file somewhere on Ubuntu that has all rights. For example odoo_auto_installer. 

sudo nano odoo_auto_installer

Then paste in the script, which you can find at https://github.com/aschenkels-ictstudio/openerp-install-scripts/blob/master/odoo-v8/ubuntu-14-04/odoo_install.sh 
Change the top variables if you want another username and password etc. be sure to change the version (line 25-26):

 #Enter version for checkout "8.0" for version 8.0, "7.0 (version 7), saas-4, saas-5 (opendays version) and "master" for trunk
OE_VERSION="8.0"

In your case you should fill in OE_VERSION="master" since V9 is still in development on Github its still master.
Then make the file executable:

sudo chmod +x odoo_auto_installer

Now that the file is executable you should execute it:

./odoo_auto_installer

This will  trigger the shell script and will automatically install and configure everything you need. When the script is done you will have a fully functional Odoo running on port 8069.

Hello Daniel,

Ubuntu is most preferred OS for Odoo.

At below link, you will find detailed steps of Odoo installation from Github Odoo branch with steps and Video. 

http://www.slideshare.net/emiprotech/odoo-v8-installation 

Hope it will help,