If you are a Fedora enthusiast, this is how you update/upgrade Fedora 18 to Fedora 19.
$ yum update yum
$ sudo yum install fedup
$ sudo fedup-cli --network 19 --debuglog /root/fedupdebug.log
$ sudo yum distro-sync
For now, the latest Fedora version is Fedora 19 Alpha release, but this update guide will also work for upgrading to Fedora final.