I don't understand what kind of change is needed to address the above observations. The user who is created at a fresh 12.04 installation is initially included in the "sudo" Unix group, which gives him or her administrative privileges. If other users are made "administrators" via System Settings -> User Accounts (which tool should be used for the purpose), they are added to the "sudo" Unix group.
Since the "sudo" and "admin" Unix groups are included in 51-ubuntu-admin.conf by default, there is normally no need to edit that file.
@Philipp: Which Unix groups are you included in? You can find out by opening a terminal window and run the "groups" command.
I don't understand what kind of change is needed to address the above observations. The user who is created at a fresh 12.04 installation is initially included in the "sudo" Unix group, which gives him or her administrative privileges. If other users are made "administrators" via System Settings -> User Accounts (which tool should be used for the purpose), they are added to the "sudo" Unix group.
Since the "sudo" and "admin" Unix groups are included in 51-ubuntu- admin.conf by default, there is normally no need to edit that file.
@Philipp: Which Unix groups are you included in? You can find out by opening a terminal window and run the "groups" command.