Cleaning up Civil 3D drawings and removing unwanted or unneeded styles has been a tedious process in the past. Yes, you could do it, but the process was time consuming. Now in AutoCAD Civil 3D 2012, we finally have a quick and easy Purge Style command. This command is found on the Manage tab of the ribbon on the Styles panel. Just run this command and you are presented with the dialog box below.
Here you are shown all of the unused styles in the drawing and can select which ones you would like to purge. You may need to run this command several times as once child styles are purged their parent styles may become unused and would then be available to be purged. It is also important to note that any styles that are set as defaults in a Civil 3D command are considered used.
This is a tool that many of us have been asking for in Civil 3D for a long time and I encourage you to give it a try next time you need to clean up a drawing.