Upgrade Ubuntu

If you want to upgrade your ubuntu version to the 12.0 ( Quantal Quetzal ) , make sure you have a working internet connection , then open your terminal or command window ( Alt+F2 ) and type
update-manager -d

The update manager will open and you will find a new box for the upgrade , click "upgrade" and relax ; it will take some time not like installing a fresh version.

This way has been useful with me for upgrading ubuntu for several versions , and I think it will be the same afterwards for upgrading for each new version for ubuntu.