There are six types of Troll written by Tolkien: See
HERE. Only the Stone trolls encountered by Bilbo and the Dwarves were mentioned to be turned to stone with the sun's light.
I would imagine that if cleverly knocked down, a nice sharp stave/spear could be rammed in between the scales of the troll's hide (An armpit would be good - puncture the lung, and if shoved far enough and at a downward angle, the heart would be pierced). Or one right through the ear hole into the brain would do it. And of course there are always the eyes . . .
~*~ Pio, the bloodthirsty