Palisades will keep most monsters out, but it will only act as a minor inconvenience to trolls. Regardless, it's ideal to surround your entire base with them to keep unwanted visitors out. As for troll raids, there's not much you can do besides maybe dig a moat or build an earthen wall with the hoe. Still, dealing with trolls is pretty easy if you have a bow and a functioning S key.

Bone piles are just enemy spawners. Attack them until they break. You have to be aggressive and break them quickly or you'll find yourself in a 1 vs infinity situation.