Interestingly, the more I use Sketchup the fewer plugins I use. For new users I suggest the following.
Start a text file in your Plugin folder, and every time you install a plugin record the following information
Name of plugin
Date of installation
List of file and folder names associated with the plugin
URL links to usage (YouTube, SketchUcation etc)
The really useful plugins will become obvious, and those you hardly ever use can be tracked and moved to a 'just in case' folder, the 'just in case' being just in case you decide you need the plugin after all.
It is important to list of the files and folders so that you remove the plugin cleanly.
Regards,
Bob