Install Firefox-Next (beta) on Mint, Ubuntu, Debian, etc…

1. Add mozilla ppa:

   $ sudo add-apt-repository ppa:mozillateam/firefox-next

2. get the ppa's origin name (bold):

   $ apt-cache policy
   ...
    500 http://ppa.launchpad.net/mozillateam/firefox-next/ubuntu/ trusty/main Translation-en
    500 http://ppa.launchpad.net/mozillateam/firefox-next/ubuntu/ trusty/main i386 Packages
        release v=14.04,o=LP-PPA-mozillateam-firefox-next,a=trusty,n=trusty,l=Official PPA for Firefox Beta,c=main
        origin ppa.launchpad.net
    500 http://ppa.launchpad.net/mozillateam/firefox-next/ubuntu/ trusty/main amd64 Packages
        release v=14.04,o=LP-PPA-mozillateam-firefox-next,a=trusty,n=trusty,l=Official PPA for Firefox Beta,c=main
        origin ppa.launchpad.net
   ...

3. Pinn the mozilla ppa for higher priority:

   $ cat /etc/apt/preferences.d/firefox-beta-pin-800
   Package:  *
   Pin: release o=LP-PPA-mozillateam-firefox-next
   Pin-Priority: 800
   

4. update/upgrade:

   $ sudo apt update && sudo apt upgrade

   ---

   Sources:

http://www.webupd8.org/2011/05/firefox-5-beta-channel-ubuntu-ppa.html

http://askubuntu.com/questions/170235/how-do-i-cherry-pick-packages-from-a-ppa