[xwiki-users] How to debug XWiki extensions

This question mainly arised from discussion about GA plugin, http://lists.xwiki.org/pipermail/users/2013-November/026937.html but I've noticed, that sometimes other extensions, e.g. http://extensions.xwiki.org/xwiki/bin/view/Extension/FullCalendar +Application http://extensions.xwiki.org/xwiki/bin/view/Extension/LiveTableExcelExport+Ma... just don't want to work. I've noticed is that sometimes warnings appear about insufficient programming rights (even for Admin) during setup, and pages just need to be re-saved to handle this. Any more steps, and tricks? Valdis