Which actions in Drupal needs clearing the cache? I'm a newbie in Drupal. I usually use the clear cache function from Devel module for each changes(sometime I use drush command line tool) like: modify CSS, create/change blocks, change permissions, create new content type, create new web form, change template files... and clearing the cache costs a lot of time on my local environment (I've just 1GB of RAM).
So can anyone show me which actions in Drupal that we need to clear cache.
Strategy is quite easy - clear it when you changed something in code or database. 

Below some popular cases (based on my experience):


you added new content and need to update cached pages, views or blocks (for example you enables cache for anonymous users)
you changed JS or CSS files and you have enabled aggregation
you installed new modules (in this case need to run update.php)
you did modifications in existing module which require update cache. For instance added menu item or implemented some hooks.
you did changes in theme files