As i was close to becoming a GM it felt like there were no more quests. It took a long time to find a quest and finally become a GM. I think we should make a book that says what side quests you can do and where. So it'll be easier to lvl up and see the quests we've missed.
They have guides on Central that detail all of the main and side quests for each world. The wiki also has pages that list most of the quests.
Other than that, the general way is to do some legwork and go back through each world and each area of that world and look for characters who need something. Since the higher-level worlds give more experience, the wizard should probably work through each world, highest-level (Dragonspyre) first.