How to get gnome shell 3.12 on ubuntu 14.04

I know there is a distro for ubuntu dedicated to gnome and I know ubuntu 14.04 comes with gnome 3.10. But I am wondering what the steps are to:

• Install the ppas for gnome 3.12
• install gnome 3.12
• only use gnome 3.12 (with no option for unity)

Note: Other answers in the similar category show getting the supported version by ubuntu, the "already packaged version" how ever there are steps to get 3.12, which doesnt come with ubuntu 14.04 and requires PPA installation.

Those steps are the steps I am looking for, not "open the software centre and download gnome" because that 3.10

You just need to install a couple of Gnome apps, add the gnome3-staging prepository and do a dist-upgrade:

sudo add-apt-repository ppa:gnome3-team/gnome3-staging
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install gnome-weather gnome-maps gnome-photos gnome-music

Via http://linuxg.net/how-to-install-gnome-3-12-on-ubuntu-gnome-14-04-trusty-tahr/

When I did this myself I got errors like these:

Error processing archive /var/cache/apt/archives/gnome-session_3.12.1-0ubuntu1~trusty1_all.deb (--unpack): trying to overwrite '/usr/share/upstart/sessions/gnome-session.conf', which is also in package gnome-session-bin 3.9.90-0ubuntu12"

Errors were encountered while processing: /var/cache/apt/archives/gnome-session_3.12.1-0ubuntu1~trusty1_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1)

To fix that if you get the same, force the package to install (which will over-write the existing gnome-session.conf file) with:

sudo dpkg -i --force-overwrite /var/cache/apt/archives/gnome-session_3.12.1-0ubuntu1~trusty1_all.deb
sudo apt-get install -f
sudo apt-get dist-upgrade