To run the JavaScript tests, first launch the development web server. Instructions on how to do so can be found in the Getting Started guide, under "Development Web Server".
Once you have launched the server, browse to http://localhost:8080/js-tests/
The full JavaScript test suite should then run automatically.
When a test fails, you can click on its test name to just run that test without running any other tests. This will better help you isolate the problem.
You can also run a subset of tests after they all pass by clicking on the desired test or ancestor in the tree of tests.
Finally, you can manually append ?spec=<path to suite> to run the specified test suite. For instance, ?spec=reviewboard admin views. Note the spaces separating the components of the suite.