It's the Characters, Stupid — Roleplaying is about interacting with other characters in a variety of ways (not just combat… not just conversation…). The choice of interaction style should always be the player's, not the designer's.

Players Do; NPCs Watch — It's no fun to watch an NPC do something cool. If it's a cool thing, let the player do it. If it's a boring or mundane thing, don't even let the player think about it — let an NPC do it.