Years of bug writing experience has been distilled for your reading pleasure into the Bug Writing Guidelines. While some of the advice is Mozilla-specific, the basic principles of reporting Reproducible, Specific bugs, isolating the Product you are using, the Version of the Product, the Component which failed, the Hardware Platform, and Operating System you were using at the time of the failure go a long way toward ensuring accurate, responsible fixes for the bug that bit you.
The procedure for filing a test bug is as follows:
Go to Landfill in your browser and click Enter a new bug report.
Select a product - any one will do.
Fill in the fields. Bugzilla should have made reasonable guesses, based upon your browser, for the "Platform" and "OS" drop-down boxes. If they are wrong, change them.
Select "Commit" and send in your bug report.