Community

I have always felt that in a world populated by adventurers, at least in the early levels, that NPC's should act and treat the PC's much like mercenaries; polite yet also cautious.

The PC's have just stumbled into town and are new faces to the other NPC's.  How friendly would you be to some passer by in the streets with a great axe over his shoulder?

But that as the quest unfolds and the PC's spend more time in the town, the NPC's would lower their guard and be more receptive.

Once paragon tier is reached, some NPC's might have heard about the heroes exploits and they might be famous in the town.  This adds another layer to leveling up.  Not only do you have better skills and abilities but you are also becoming known within the game world.

I like the idea that the NPC's can be more than simple quest givers.  That NPCs can give PCs a lot more than a map of the area and a goal for the next few weeks.  NPCs should be the DM's PCs.  If the DM has the ability to make interresting scenerios that involve the NPC interracting with the players it will make that NPC memorable and make the quest more than simply an excuse to roll dice.