Following the D&D logic cut them, then cauterize the wound with acid or fire so they cant regenerate. They are very weak against fire and acid.
However, since it is an absolute crime to just pour acid on trolls or burninate them, Best to just starve them.. That's right, trolls feed on the attention of others, they are sad pathetic creatures that need to be the center of attention. So deal with them with a solid axe in the game, then on the forums, Ignore them.