Players solve quests. So what? Why they do that, what kind of quests there must be, what do players gain from quests, what keeps them doing more quests? To gain something. What? Wealth. Knowledge. (Friends?) Where they could go? And what to do there? Hmh. There is several gategories: Get, Protect, Carry, Tell, Kill, Destroy, Find, Help.. (etc) Use imagination to say it in more detail.