We have above an NPC's head to show they have a quest for you, and to show they're part of a quest goal, but what about plain ol' dialogue. Sometimes, the dialogue can be helpful, especially for beginner players. I was thinking a new sign should be added above NPCs who don't have a quest to give you and/or aren't part of a quest goal, but simply say dialogue, especially for those that give good tips.
I like this idea, P101 has something similar This will help new players greatly. But also diego the duelmaster should have a tab for reviewing his tutorials, just in case you forget
above an NPC's head to show they have a quest for you, and 
to show they're part of a quest goal, but what about plain ol' dialogue. Sometimes, the dialogue can be helpful, especially for beginner players. I was thinking a new sign should be added above NPCs who don't have a quest to give you and/or aren't part of a quest goal, but simply say dialogue, especially for those that give good tips.