I have tried the standard:
apt get install update-manager-core do-release-upgrade
but this does not seem to get it to 14.04 LTS.
Are there other steps that I am missing?
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LTS-to-LTS upgrades are always delayed until the first dotrelease (service pack) is ready. The larger differences between the two LTS versions means they need more time to get it right.
In your case, you'll be presented with an option to upgrade when Ubuntu 14.04.1 is released, which is scheduled for July 24th 2014.
As Jo-Erlend Schinstad mentioned they are somewhat delayed while some bugs that normally appear on the first days are solved. If you still want to migrate then you can do it this way:
sudo update-manager -d
sudo do-release-upgrade -d
Be aware that if you used 3rd party PPAs or even some type of packages that add their own repositories, this procedure will fail at the end and will not update your system. You would have to upgrade the system using a LiveDVD or LiveUSB in which case, in the Ubuntu installer it will say "Upgrade Ubuntu 12.04 to Ubuntu 14.04".
On both cases, downloading the ISO or upgrading, the upgrade will be huge because of the many packages that have changed so it will take a bit of time.