You should have a recent version of KDE, preferably trunk or the beta 1 release. You can still help if you only have the 4.5.3 release though.
Some packagers provide LiveCD/DVDs to faciliate testing:
For some distributions pre-compiled and -packaged versions of trunk or the beta are available in additional repositories, ready for consumption:
Prioritizing is good. If a major application doesn't work, this should be taken care of.
After adding triaged bugs on this page, you should keep an eye on their bugzilla status. Add yourself on the CC field in bugzilla to be informed about updates. When a bug is closed on bugzilla, it should be updated on this page.
You can do this with the tag <s>...</s>