Test the latest installer
With a spare laptop or workstation (or just a virtual guest), you can provide feedback on how the installer is doing by sharing results on https://fedoraproject.org/wiki/Test_Results:Fedora_12_Pre-RC_Install. The installer continues to improve since the beta. Take a look at recent anaconda changes for a change that may impact your system(s).
Test a bug fix
Help a maintainer by verifying a recent bug fix. A good place to start is by choosing a MODIFIED bug from the F12Blocker list. The list of MODIFIED bugs will be growing as issues are triaged and patches come in.