Make small quests where people just accept a quest and have to talk to another NPC in another place to complete it and add small rewards every time. You could make them go to towns but also to places such as the battle arena or master li's, pirate bay quest, taylor richaards and so on. When you complete your quest at one NPC it would give you a quest to the next. There could be a symbol with the NPC's location on the map.