Quests are generated randomly the first time you speak to a Quest Manager. You will always get a Delivery and an Elite quest, and four others randomly picked between Hunt and Gather that both work fairly similarly. All Quest Managers are the same. You can start a quest at any of them and complete it at any of them. Depending on the quest type and the amount of mobs or items needed, you will get 1-4 Guild Coins upon completion of any quest.