There is a site called Runehq it has everything about Runescape even what monsters drop check it out. : -)
Monsters drop them. As a general rule, higher level monsters drop better things.
hill giants and hobgoblins drop them sometimes
Monsters in the god wars dungeon drop them. They're really hard to beat though.
No, but only certain NPC's, monsters will drop them.
Killing druids in taverly dungeon is probably the best place to get any herbs, they drop more that most monsters do.
When I trained range on fire giants i got like 100 blue charms or more their not likely to appear though that's just one of the monsters that drop them try going to a runescape help site and type in monsters that do drop blue charms.
You have to fight certain monsters in the Stronghold in the Barbarian village until they drop the pieces... there's a piece on every floor of it, and only certain monsters drop them...
I do not know the complete list however, I do know that these monsters do drop law runes: barbarians dark wizards wizards cockroach soldiers
Dust Devil and Kalphite Queen members only.
Its a rare drop from certain monsters and requires level 91 of the skill to use.
steel or iron dragons.. there are others just these are a couple i know