There is no blatant way to tell. At your best bet, if you are lost, just look up the main storyline online, and find where you're currently at. Usually the article will provide in depth detail about the quests, etc. to help with your concerns.
If you have the option to decline the quest or accept it, then it's a side quest. If you can't decline the quest, that means it's a storyline quest because it's mandatory to do in order to get closer to moving on to the next world.
If you have the option to decline the quest or accept it, then it's a side quest. If you can't decline the quest, that means it's a storyline quest because it's mandatory to do in order to get closer to moving on to the next world.
I think they meant from when choosing a quest within their book, etc.
