I'd like to make a web page for content authors to clear cache, without giving their group access to Utilities in the CP. So I'll have to manually clear cache. Is it as easy as clearing what's in system/user/cache? Or would it be better to do this another way?
You could allow the authors member group access to System utilities, you can restrict it so they only have access to "Data operations" which has the clear cache facility. Also add a custom menu link directly to that page for quick access.
If you wanted to do it manually delete all the content inside /system/use/cache/default_site