I'm looking for a general guide for public photography. Is there a set of regulations that applies to various kinds of locations? Any recommendations on where to go first to begin obtaining licenses in other countries?
I believe you were given some indications when you posed the question; you can view them, but I will offer some instances for your convenience that have been covered in depth before.
Additionally, your point. Beyond the obvious, I'm not sure what you're saying. The point is, You do need permission to enter someone's private property; that is true. That is a no-brainer, regardless of whether or not taking photographs is so unimportant to photography and is a universal action to avoid being shot.
Although it mostly concerns commercial photography, some information applies to everyone.